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Mammographic feature analysis
Mammographic Feature Analysis By Carl J. D'Orsi and Daniel B. Kopans
DR. Albert Salmon first reported on I Nthe1913,effectiveness of radiographic technique as applied to mastectomy specimens to demonstrate differences in the margins of invasive and circumscribed breast carcinoma. 1 Eighty years later, skepticism from some of our clinical and epidemiological colleagues concerning the efficacy of mammography persists. Often this attitude is fostered by a lack of knowledge of the goals and limitations of mammography as well as by the multifaceted problems of breast cancer in our society. With the realization that one out of nine American women will develop breast cancer in their lifetime2 and that breast cancer is the second leading cause of cancer mortality,3 attention has been directed toward mammography as the best means of detecting preclinical breast malignancy. This concept has been repeatedly justified in randomized screening trials.4-6 The importance of quality assurance in any mammography-based screening program has developed in a parallel manner as substantiated by the Canadian National Breast Cancer Screening Study7,s and critiques of their technique. 9 Currently the best available mechanism for obtaining high-quality mammography is referral of women to facilities where the mammographic equipment is accredited by the American College of Radiology. Passage of the Federal Mammography Quality Standards Act of 1992 and establishment of a panel by the Agency for Health Care Policy and Research to determine
ABBREVIATIONS BIRADS, Breast Image Reporting and Data System; CC, craniocaudal; DCIS, ductal carcinoma in situ; MLO, mediolateral-oblique.
From the Department of Radiology, Universityof Massachusetts Medical Center, Worcester, MA; and the Department of Radiology, Harvard Medical School, Boston, MA. Address reprint requests to Carl Z D'Orsi, MD, Professor, Department of Radiology, Universityof Massachusetts Medical Center, 55 Lake Ave North, Worcester, MA 01655. Copyright 9 1993 by W.B. Saunders Company 0037-198X/93/2803-000555.00/0 204
quality standards for mammography reinforce the interest in mammography not only from a medical standpoint but from social and legislative perspectives as well. The orientation of this communication differs from other articles on mammography. Ordinarily, findings for malignant and benign conditions are presented using the various pathological entities to introduce and describe associated mammographic findings. However, in daily medical practice mammographic findings and details of their features ultimately guide the recommendations and outcome whereas the actual pathology assumes a secondary yet still important status. This article is divided into sections on technique, masses, calcifications and associated findings, new and/or developing findings, recommendations, and localization. Findings and their definitions are those recommended by the newly established American College of Radiology Breast Imaging Reporting and Data System (BIRADS). They are illustrated by line drawings alone, both line drawings and mammographic examples, or solely by mammograms. Each section on mammographic features attempts to discriminate relatively benign from malignant features. The ultimate decision to obtain tissue, short-term follow-up, or other imaging procedures (such as ultrasound) must be based on a clear understanding of mammographic findings and experience. Asymptomatic women and those with signs or symptoms related to the breast can benefit from breast-imaging studies. The major role for mammography is the early detection of breast cancer in asymptomatic women. The efficacy of screening has been established by randomized trials in which absolute mortality has been reduced. Although mammography can detect the majority of breast cancers, some lesions may elude mammographic detection and yet be palpable. Thus an important component of screening is the physical examination provided by the referring physician or the screening facility. Mammographic screening involves the performance of standard projections, usually the meSeminars in Roentgenology, Vol XXVIII, No 3 (July), 1993: pp 204-230
Fig 1. Compression effect. CC view (A) demonstrates a focal density (arrow}, which loses its mass-like appearance w i t h a compression view (B).
Fig 2.
Round and oval mass. Line drawing of round (A) and oval (B) mass. Fibrodenoma.
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diolateral-oblique (MLO) and craniocaudad (CC) views. 1~ In some settings, additional images are undertaken immediately to solve a question, and in other settings, the patient is recalled for further evaluation. Mammography may be coupled with other breast-imaging techniques (such as ultrasound) for evaluation of women with a sign or symptom suggesting cancer. Although this diagnostic mammogram may not influence clinical care, the study is still important to evaluate the clinical lesion as well as to screen the remaining ipsilateral and contralateral breast. Just as clinical decisions may be made solely on mammographic suspicions, the negative mammogram in the setting of a clinical abnormality must not deter or delay management. TECHNIQUE
Earlier detection of breast cancer using mammography requires a well-organized and systematic examination. High-quality imaging requires accredited, dedicated mammography equipment that is carefully maintained with appropriate quality controls. The technologist performing the examination must be well trained and skilled in proper positioning. Appropriate exposures are required using low-kilovolt (peak) techniques. The film processor should be optimized for mammographic film, and the quality control program should be carefully tailored to maintain optimum film development. A detailed description of these parameters can be Fig 4. Irregular mass. Medial oblique (A) and magnification compression-spot view (B) demonstrate an irregular mass with angular protrusions. Note benign, round calcifications within the mass. Infiltrating ductal carcinoma.
Fig 3. Lobulated mass. Lobes (arrows) from well-circumscribed mass. Fibroadenoma.
obtained from the American College of Radiology. Mammograms should be read on view boxes that arc masked to exclude extraneous light and glare from around the images. The breasts should be considered symmetrical organs, and the mammograms should be positioned on the view box to take advantage of this symmetry in a search for asymmetry. Position mammograms in the same orientation at all times so that left-right confusion is minimized. Once an abnormality has been detected, it
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Fig 5. Circumscribed. Sharp definition between margin and surrounding tissue.
must be properly characterized by careful analysis of its mammographic features. Various mammographic maneuvers allow one to determine the three-dimensional findings. This initial step is important because numerous overlapping structures in the breast form normal summation shadows that can mimic true abnormalities.
Fig 6. Microlobulated margin. Line drawing (A) of irregularity of the margin raising the possibility of invasion, Magnified compression-spot view (B) of microlobulated margin (arrows). Invasive intraductal carcinoma.
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The two main radiographic maneuvers to aid in detection and characterization are different views and/or obliquities and tailored compression. Our first task is to verify a finding, considering that the breast presents an ideal background both to create and camouflage findings. The 90~ view, exaggerated axillarycraniocaudal view, roll view, and spot-compression view are extremely useful toward this end. The task is to differentiate adjacent tissues from each other by changing their relationship. In summation shadows caused by overlapping glandular tissue, varied views allow a confident appraisal of such densities. In the case of true findings, little change in appearance occurs with these views. The magnification spot-compression view allows a more critical analysis of the margin of a mass and the morphology of calcific elements. If a palpable mass is present, a tangential view, placing the mass in profile, will often delineate and/or enhance the margins. These mammographic maneuvers are used to
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both verify and characterize mammographic findings. The implant-displaced technique pioneered by Ecklund 11 allows the technologist to posteriorly displace the implant with a compression paddle while simultaneously pulling breast tissue on the film cassette. This maneuver delineates more breast tissue in an optimal manner. However, at the same time no maneuver with
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the implanted breast will allow as much tissue visualization as the breast without implants. MASSES
Because the breast is composed of glandular and fatty tissue in random distributions, false projection of what appears to be a mass is a possibility. This appearance is termed a summation artifact and is often resolved by the use of
Fig 7. Obscured margin. Line drawing (A) highlights absence of a margin owing to adjacent glandular tissue. This may be considered a mammographic "silhouette" sign. The obscuration is suggested on the mass observed in the medial oblique view (B) (arrow) and emphasized on the magnification compression-spot view (C), demonstrating glandular tissue (short arrows) obscuring the margin that is well-observed in an adjacent area (large arrow). Similar findings on a second case (D) show glandular tissue (large aYrows) obscuring a portion of the margin (small arrows).
MAMMOGRAPHIC FEATURE ANALYSIS
orthogonal and spot-compression views (Fig 1). A true mass is a space-occupying lesion persisting in two different projections after appropriate evaluation is completed. A possible mass observed in only a single projection should be called a density until its three dimensions are confirmed. In order to successfully recommend appropriate management, several features of the mass should be evaluated. A description of the shape, margin, and density allow an orga-
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Fig 8. Indistinct margin. CC v i e w (A) demonstrating mass with almost completely circumscribed margin. However, magnification spot-compression v i e w (B) shows an indistinct margin (arrow) with no adjacent glandular tissue, Secretory carcinoma.
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nized analysis and recommendation. With standardized language, an analysis is understandable to both clinician and radiologist. The shape of a mass may be categorized as round, oval, lobulated, or irregular. The round mass is spherical or globular and the oval mass is elliptical (Fig 2). The lobulated mass (Fig 3) has contours with undulations that may indicate a degree of autonomy. Finally the irregular mass (Fig 4) is one whose shape cannot be described
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by any of those ~previously defined. The latter indicates the most worrisome situation as far as shape analysis is concerned. The margin characteristics of a mass observed mammographicaily are the major determinants of its benign or malignant status. The circumscribed (well-defined or sharply defined) mass is one whose margins are sharply demarcated with an abrupt transition between the lesion and surrounding tissue. Without additional modifiers, nothing in this appearance suggests infiltration (Fig 5). A microlobulated margin has an edge that undulates with short cycles and may indicate microscopic invasion of surrounding breast tissue (Fig 6). Obscured margins are hidden by superimposed or adjacent normal tissue and cannot be assessed any further (Fig 7), and an indistinct margin indicates that poor definition of the edge is not likely due to superimposed breast tissue and thus raises the concern of infiltration by malignancy (Fig 8). Finally, a mass with fine lines radiating from its margins is said to be spiculated and is the most suspicious margin feature for malignancy (Fig 9).
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Fig 10. Fat-containing mass. Lucent mass (arrow) with thin wall in an area of previous surgery. This is most compatible with a traumatic lipid cyst,
The density of a mass is probably most difficult to accurately a c c e s s . 12,13 Although singularly it may not be a powerful discriminator between benign and malignant, taken with other
Fig 9. Spiculated margin. Medial oblique view (A) demonstrating mass (arrow) with spiculations. The magnification spotcompression view (B) more clearly demonstrates the fine nature and radial orientation of spiculations (small arrows). Invasive ductal carcinoma.
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features of a mass, the density assessment can be extremely useful. The X-ray attenuation of a mass is related to the attenuation of an equal volume of fibroglandular breast tissue. Breast cancers are most often of equal or higher density than glandular elements. Thus a highdensity mass is one that is conspicuous owing to increased radiographic attenuation, and a lowdensity mass is conspicuous for diminished attenuation compared with approximately equal volumes of glandular tissue. The equal or isodense
Fig 11. Dilated duct. There is a tubular density in the left CC view from 1989 (A) (arrow). There are no clinical or associated mammographic features to imply malignancy. A similar view on a follow-up examination in 1990 (B) does not demonstrate the tubular structure.
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mass is approximately equal in attenuation to surrounding glandular elements. Of special interest is the fat-containing or radiolucent mass. This category includes all lesions containing fat, such as lipid cysts, lipomas, and galactoceles as well as mixed lesions, such as hamartomas (Fig 10). Because there are no reported examples of fat-containing breast malignancies, the importance of this finding is obvious. Several special cases cannot be strictly catego-
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Fig 12. Intramammary lymph node. Lobulated, circumscribed mass with central lucency (arrow).
rized with masses. The tubular density most likely represents an enlarged duct. If unassociated with other suspicious clinical or mammographic findings, a tubular density usually has minor significance (Fig 11). Intramammary lymph nodes are typically reniform, have a radiolucent notch due to fat at the hilum, and are generally 1 cm or less in size. They may be larger than 1 cm when fat replacement is pronounced. Multiplicity or marked fat replacement may cause a single lymph node to resemble several rounded masses. This specific diagnosis should be reserved for masses in the axillary and superior portion of the breast, although on rare occa-
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sions they may occur in other areas of the breast (Fig 12). 14-16 Asymmetric breast tissue is judged relative to the corresponding area in the contralateral breast and includes a greater volume or density of breast tissue and ducts. The area frequently assumes different shapes on orthogonal views. This usually represents a normal variation but may have greater significance if it corresponds to a clinical finding (Fig 13)) 7-19Focal asymmetric tissue cannot be accurately described using the previously described shapes. Although asymmetric, these lesions may be observed on two views with a similar shape but not as conspicuous as a true mass and lacking the defined margins of a mass. Focal asymmetric tissue may represent an island of normal breast tissue, but its lack of specific benign characteristics may warrant further evaluation. Additional imaging may show a true mass or other significant features. Architectural distortion includes spiculation radiating from a point with no definite mass visible (Fig 14). This appearance can also include focal retraction or distortion of the edge of the breast parenchyma. Architectural distortion may also be associated with a mass.
Differential Considerations for Masses Although listing all the possible combinations of shape, margin, density, and special cases and their significance is not practical, several examples are presented here to demonstrate how mass-feature analyses can significantly contribute to formulate pertinent management options. The round or oval, well-circumscribed mass of equal or low density a n d / o r fatcontaining mass has all the criteria of a benign mass. An irregular mass with spiculated margins
Fig 13. Asymmetric breast tissue. Line drawing of nonfocal asymmetry (highlighted area) displaying different shape between the CC and MLO views.
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Fig 14. Architectural distortion. Line drawing (A), CC view (B), and medial oblique view (C) demonstrate the area of distortion (large arrows) (B and C) with fine radiating lines converging to a single region with no mass formation (small arrows) {B). Invasive ductal carcinoma.
or an area of architectural distortion has significant criteria for malignancy. 2~ At the same time, an important caveat must be added with architectural distortion and to a
Fig 15. Architectural distortion. CC (A) and MLO view (B) depicting distorted anatomy and fine spiculation (small arrows) unassociated with a mass. Note the lucent area (large arrow) centrally placed within the distortion secondary to fat necrosis. Prior surgical biopsy.
lesser extent with spiculated masses. Intramammary scar tissue a n d / o r fat necrosis from surgical or nonsurgical trauma may mimic the architectural distortion associated with malignancy
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D'ORSI AND KOPANS Table 1. Malignant Potential. Mass Feature Analysis Features
Shape Round Oval Lobular Irregular Margins Circumscribed Microlobulated Obscured Indistinct Spiculated Density High Equal Low Fat containing Special Cases Solitary dilated duct Intramammary lymph node Asymmetric breast tissue Focal asymmetric density Architectural distortion
Benign/ Indeter- Suspicious/ Probably Benign minate Highly Suspicious X X X X X X X X
X X X
X X X
X
X X X
X X X
Fig 17. Early vascular calcification. Heterogeneous elements of calcification with a straight tubular distribution (arrows). Although these calcifications do not definitely demonstrate parallel tracks of calcification, their tubular arrangement and long linear course suggest vascular calcification.
(Fig 15). Although the breast often heals with little mammographically visible abnormality after a biopsy, with the increased use of biopsy for nonpalpable findings as well as conservative therapy for early breast carcinoma, we can expect postsurgical or traumatic architectural distortion to increase. 21,22
Fig 16. Dermal calcifications. Rim calcification (arrows) located adjacent to the inferior, posterior skin margin. This represents a typical appearance and location for dermal calcification.
Fig 18. Popcorn calcification. Extremely coarse calcifications often occupying all of an involuted fibroadenoma.
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a biopsy siteY Table 1 lists mass features and their malignant potential. CALCIFICATIONS
Mammography is the only examination that can consistently identify calcification within the breast, which can signify early malignancy. Leborgne 26 described calcification in terms still in current use. When reporting on calcification it is important to describe the morphology of each element of calcification as well as their distribution within the breast. Certain calcifications are almost always benign whereas others are of intermediate and great concern. Distribution modifiers also require assessment.
Typically Benign Calcification
Fig 19.
Large rod-like calcifications. Numerous coarse lin-
ear calcifications (arrow) oriented toward the nipple,
Architectural distortion from malignant and nonmalignant causes is virtually indistinguishable. A baseline mammogram 2 to 3 months after surgery on the involved side may preclude the need to rebiopsy. 23,24A round, lucent area situated in an area of architectural distortion after surgical intervention may allow a more confident diagnosis of traumatic lipid cyst within
Calcification does not always need to be noted in the mammography report but should always be reported when the radiologist is concerned that it might be misinterpreted by other observers. Skin calcifications are typically lucent-centered deposits around the areola, axillary or medial, and inframammary portions of the breast. When in these locations with lucent centers, they are pathognomonic (Fig 16). Calcification with atypical elements and/or locations may be confirmed as dermal by tangential views. 27-29 Vascular calcifications occur as parallel tracks or linear tubular calcifications that are clearly associated with blood vessels. Difficulty may arise in characterization during the initial phases of vessel calcification. Magnification views and
Fig 20. Round/punctate calcifications. Round (A) and punctate (B) calcifications distributed in a diffuse manner. The morphology of the elements is similar and differs only in size.
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films with slightly different obliquities are often helpful (Fig 17). Fibroadenomas, as part of involution, frequently calcify with a coarse or popcorn appearance (Fig 18). However, initial calcification may be finer and difficult to distinguish from those caused by cancer. Large rod-like calcifications are benign. These calcifications form continuous rods that are
Fig 21. Lucent-centered calcifications. Fairly thick rim (arrow) with lucent center.
Fig 22. Rim (eggshell) calcifications. These are benign forms of calcification often occurring in cyst walls, Magnified view of rim calcifications.
Fig 23. Milk of calcium, MLO view (A) with oval mass and partially obscured margins (large arrow), Small area of slightly increased density projected within the mass (small arrow), Ninety-degree lateral view (B) again demonstrating mass (large arrows). Linear ca|cific density (small arrow) representing movable calcific particles within large cyst.
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occasionally branching and usually 1 mm or more in diameter. They may have lucent centers if the calcium surrounds rather than fills the ectatic duct or if the intraductal debris is incom-
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pletely calcified. This is the type of calcification found in secretory disease and duct ectasia (Fig 19). Round calcifications may vary in size and are
Fig 24. Suture calcification. Line drawing of retained, unabsorbed suture material (A). MLO view with linear arrangement of calcified suture material.
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usually considered benign. When under 1 ram, they are frequently formed in the acini of lobules. When under 0.5 mm, the termpunctate may be used (Fig 20). Spherical or lucent-centered calcium deposits may range in size from under 1 mm to over 1 cm or more. They are smooth and round or oval
Fig 26. Amorphous calcification. Magnified views (A and B) of t w o separate clusters of indistinct calcifications. These forms are often at the limit of visibility owing to their diminished density. Both areas were removed and were benign without pathological risk factor for malignancy.
Fig 25, Dystrophic calcification. Coarse, irregular calcification posteriorly and inferiorly placed. Patient with a transverse rectus abdominis myocutaneous flap reconstruction.
with a lucent center. These deposits often develop in areas of fat necrosis, within ectatic ducts, and occasionally in the early phase of degenerating fibroadenoma (Fig 21). When the wall of these lucent-centered calcifications is thin, usually well under 1 mm, the term rim or eggshell calcification may be used (Fig 22). Calcification in the wall of cysts are the most common cause of rim calcification.
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The varying appearance of calcifications on different mammographic projections is typical for milk of calcium. On the CC image, they are often less evident and appear as fuzzy deposits, yet on the horizontal beam-lateral they are sharply defined with a semilunar, crescent, or linear configuration. This appearance is compatible with sedimented calcification within cysts that defines the dependent portion (Fig 23). 30'31 Suture calcifications are the consequence of calcium deposition on suture material and are relatively common in the breast treated conservatively for breast cancer. They are typically linear or tubular in appearance, and knots are frequently visible (Fig 24). 32 Dystrophic elements usually develop after trauma or irradiation. Although irregular in shape, they are usually over 0.5 mm in size and often have lucent centers (Fig 25). 33
Calcifications of Intermediate and Great Concern These calcific elements range from those that are probably benign to those highly suggestive of malignancy. After mammographic evaluation, they frequently require further characterization in the form of follow-up or biopsy. Amorphous or ind&tinct elements are often round or flake-shaped calcifications that are sufficiently small or hazy in appearance that a more specific classification is impossible (Figs 26 and 27). Pleomorphic or heterogeneous granular calcification may have a morphology similar to the amorphous forms but is denser and more conspicuous. The forms are irregular with varying sizes and shapes and are usually less than 0.5 mm in size (Fig 28). Fine and/or branching linear (casting) calcifications are thin, irregular calcifications that appear linear but are discontinuous and under 0.5 mm in width. Their appearance suggests luminal filling of a duct involved irregularly by breast cancer (Fig 29).
Distribution Modifiers Not only is calcific-element morphology important but the arrangement of the calcific elements may provide clues for further management. Grouped or clustered calcifications occupy a relatively small volume (less than 2 cc) of breast tissue (Fig 30). Linear calcifications are arrayed in a line with or without branch points
Fig 27. Architectural distortion and amorphous calcification. There is focal retraction at the edge of the breast parenchyma (A) (arrow). Magnification compression-spot view (B) enhances the architectural distortion (curved arrow) and also demonstrates a cluster of amorphous calcifications (straight arrows), Invasive ductal carcinoma,
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Fig 28. Pleomorphic-heterogenous calcification. These are similar in appearance to the amorphous forms but are much denser and more conspicuous. Line drawing (A) and magnified view (B) (arrow) of typical appearance. The morphology, clustered distribution, and large numbers of caicific elements (B) strongly suggest malignancy. Moderately differentiated invasive ductal carcinoma.
A
Fig 29. Fine and/or branching linear (casting) calcification. Line drawing (A) and magnified image {B) (arrow) show thin, irregular linear branching elements arranged in a cluster. Specimen radiograph (C) (arrow) depicts calcific morphology to better advantage. Invasive ductal carcinoma and DCIS.
Fig 30. Clustered calcifications. Heterogeneous calcifications are distributed in a small volume of tissue (large arrows). Note the coarse (popcorn) calcification (curved arrow). Involuted fibroadenoma and intraductal hyperplasia.
Fig 31. Linear distribution. Heterogeneous calcification (A) (arrows) is oriented in a linear manner over a short distance and does not conform with a tubular density. Multiple foci of intraductal carcinoma, comedo type. Punctate and heterogeneous calcifications (B) (arrows) are distributed in a branched linear pattern. Intraductal carcinoma.
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Fig 32. Segmental distribution. Distribution is not as confined as clustered or linear patterns and suggests involvement of more than one ductal system.
(Fig 31). This appearance increases concern because the arrangement suggests a ductal origin. A variation of the linear distribution is segmental, which suggests deposits in multiple ducts and their branches and raises the possibility of multifocal malignancy. Although benign causes of a segmental arrangement exist, such as secretory disease, this distribution should provoke greater concern when the morphology of the calcific elements is not specifically benign (Fig 32). Calcifications prevalent in a large volume of breast tissue not necessarily conforming to a duct distribution but not affecting all areas of the breast are regional in distribution (Fig 33). Diffuse or scattered calcifications are distributed randomly throughout the breast (Fig 34). Multiple groups of calcifications indicate more than
Fig 33. Regional distribution. This pattern is more extensive than a segmental distribution but not as disseminated as a diffuse distribution.
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Fig 34. Diffuse/scattered distribution. The calcific elements in this pattern are randomly distributed.
one group of elements similar in morphology and distribution (Fig 35). Multifocal areas of malignancy presenting as identical groups of calcification occur infrequently. However, we must assure that the element anatomy is not suspicious and that all groups are similar in appearance.
Differential Considerations for Calcification Once analysis and description of microcalcification and its distribution is accomplished, the much more difficult task of management begins. We have tried to differentiate management on the basis of benign or malignant potential. An excellent source of material to gain confidence in this endeavor is one's own biopsy material. Review of cases with assignment of an estimate of malignant potential (1 for benign, 5 for malignant) allows for a semiquantitative score
Fig 35. Multiple groups. Calcifications of similar element shape and distribution indicate similar pathology. Multiple clusters of round calcifications are depicted in the line drawing.
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Table 2. Malignant Potential. Calcification Feature Analysis Features
Elements Typically benign Amorphous Heterogeneous Linear/branching Distribution Cluster Linear Segmental Regional Scattered/diffused Multiple groups
Benign/ Indeter- Suspicious/ Probably Benign minate Highly Suspicious
X
ASSOCIATED FINDINGS X
X X X X X
strates features of calcifications with their malignant potential.
X
of performance. This exercise will help demystify the management process and also serve as an invaluable teaching aid. Using biopsy material, Ciatto and colleagues 34 demonstrated that punctate calcifications are infrequently associated with malignancy whereas heterogeneous, fine branching linear calcification has a high predictive value for malignancy. In a double-blind study conducted by Stomper et al, 35 comedo types of ductal carcinoma in situ (DCIS) are accompanied by linear-branching calcification, and noncomedo DCIS is more often associated with heterogeneous (granular) elements. Similar information is presented by Roses et al. 36 In their study group biopsied for microcalcification, 95% had malignancy when more than 10 linear calcifications were unassociated with a mass or at least 1 linear calcification was associated with a mass. Conversely, punctate calcifications were benign. Table 2 demon-
Associated findings are usually found in conjunction with masses and/or calcifications, but they may stand alone as primary findings when no other abnormality is present. Skin and nipple retraction (Fig 36) is an abnormal tethering or pulling in of the skin or nipple. When associated with masses and/or indeterminate calcification, retraction is an ominous sign. Benign skin retraction often occurs in an area of prior biopsy. By marking visible scars on the skin of the breast, this cause of retraction can often be determined. Nipple retraction assumes importance as an isolated finding when the onset is recent. Skin thickening may be focal or diffuse. When associated with suspicious masses, calcifications, or clinical findings of inflammation, thickening indicates dermal lymphatic obstruction. Biopsy scars may also produce thickened skin. Radiation therapy, generalized edema, and inflammatory carcinoma may all produce a generalized thickening of the skin around the breast. 37 Trabecular thickening indicates enlargement of the fibrous septa of the breast and is found in many of the same conditions as diffuse skin thickening (Fig 37). Skin lesions (Fig 38) should be marked before filming the breast. They may be mentioned when projected over the breast in two views and possibly mistaken for an intramammary mass. Enlarged, nonfatty replaced
iLii
/
A Fig 36. Nipple/skin retraction. Nipple retraction assumes more importance when associated with recent onset and/or a mammographic finding (A). Skin retraction (B) is often observed after surgery with advanced breast cancers and with malignancies immediately adjacent to the skin.
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Fig 38. Skin lesion. Mention of a skin lesion may be useful if it is projected within the breast on t w o different views. Lucency that sometimes surrounds a skin lesion is probably secondary to surrounding air.
prior examination. With the increased use of estrogen-replacement therapy, nonfocal diffuse changes in glandular tissue may be observed. 38 Invasive lobular carcinoma may present as an asymmetric density with none of the typical
Fig 37. Skin and septal thickening. Skin thickening (large arrows) with increased thickness and conspicuity of septa (small arrows) 3 months after surgery and radiation therapy.
axillary lymph nodes may be noted in the report, although mammographic assessment of these nodes is unreliable (Fig 39). NEW AND/OR DEVELOPING FINDINGS
Although difficult to categorize, new or developing changes are of utmost importance, especially for detection of early, subtle malignancy. The analysis requires comparison with prior examinations whenever possible. Of greatest concern are mammographic findings that change over a relatively short period of time and findings that are new when compared with a recent
Fig 39. Axillary nodes. Nodes that are greater than 1-1.5 cm, are without fatty replacement, and are matted, as depicted in the line drawing, are most suspicious for malignancy.
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features of malignancy. Often the only possibility for determining its malignant nature is careful comparison with prior studies (Figs 40 through 43). 39 Analysis of interval carcinomas
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(carcinomas arising in the interval between scheduled mammographic screens) from the Malmo Screening Trial reinforces the need for comparison. In slightly fewer than 50% of pa-
Fig 40. Developing density. CC view from 1991 (A) shows no definite finding suspicious for malignancy. On routine follow-up in 1992, the CC view (B) shows a subtle change (arrow), which on magnification compression-spot view (C) fails to change its appearance (arrow). Invasive Iobular carcinoma.
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Fig 41. Developing density. Mediolateral oblique view (A) from 1987 suggests an irregular mass (large arrows) and spiculation (small arrows), but this appearance may be simulated by overlapping densities. No further work-up was conducted. Patient failed to return for mammography until 1992 (B), when mammogram demonstrates progression and increased conspicuity of the irregular mass (large arrows) and spiculation (small arrows). Invasive ductal carcinoma.
tients, a change owing to subtle growth was noted when examinations taken at discovery of the interval cancer were compared with the immediately prior examination. 4~ In Sickles 41 article on mammographic follow-up, 15 of 17 malignancies were identified by interval mammographic changes with 10 of 15 found between 6 to 18 months of follow-up.
RECOMMENDATIONS
Once analysis of the findings takes place, recommendations and management decisions must be made. The American College of Radiology BIRADS system was designed to ensure that ultimate breast-imaging assessment was decision oriented. Two major categories of assessment are available.
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Fig 42. New density. The right CC view from 1989 (A) demonstrates no features indicative of malignancy and appears similar to the left CC view. In 1991 (B), the density is markedly increased in the subareolar area, which on magnification compression-spot view (C) fails to show any specific malignant features. Thus, the only clue for the presence of carcinoma is subareolar asymmetric breast tissue occurring over a 2-year interval. Infiltrating ductal carcinoma.
In the screening situation, where the only decision relates to normal or abnormal, the BIRADS system recommends routine examination or additional evaluation for patients with positive studies. When findings have been thor-
oughly investigated, a more complete recommendation is required. In a negative examination, no abnormalities or other findings are noted and the breasts are symmetric. A benign status is also negative, but the interpreter may describe a
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finding, such as typical involuting calcified fibroadenoma, multiple secretory calcifications, or fat-containing masses. The probably benign category is reserved for findings that have a high probability of being benign. These are not expected to change, but the radiologist may prefer to establish their stability by recommending an initial 6-month short-term follow-up. Data are now becoming available 42-44 on the efficacy of short-term follow-up. A suspicious abnormality has features without characteristics of breast cancer but with a definite probability of malignancy, and the radiologist has sufficient concern to urge a biopsy. The highly suggestive findings are those with a high probability of representing cancer. When conveying information either verbally or in a report, communication of the radiologist's level of concern and recommendations for future patient assessment is critical. LOCALIZATION
Fig 43. New calcifications. Magnification compressionspot view from 1989 (A) shows a single coarse, branched calcification (curved arrow). On follow-up 1 year later (B), the coarse calcification is stable (large arrow), but new fine, linear branching calcifications are present (small arrow). Ductal carcinoma in situ.
Although not completely within the scope of this article dedicated to mammographic feature analysis, it is important to outline the basic technique and principles related to localization of nonpalpable mammographic findings. All of the available localizing devices are based on the design of a hooked or curved wire placed within a needle for introduction. The choice of device is relatively unimportant as long as the target is routinely removed. Failure rates of about 5% have been reported. 45,46 Of primary concern is to ensure that the finding is not artifactual and is located within the breast. This assumes a thorough work-up of any findings before a recommendation for localization. Particular attention should be paid to calcifications adjacent to a skin surface on one or more views. If a dermal location is suspected, a tangential view should be obtained. 47 After verification and work-up of a suspicious abnormality, the plan for localization should be formulated before the day of surgery. The shortest distance to the target should be chosen as the point of entry for the localizing device. This must not include insertion directed toward the chest wall. Thus we have four choices: (1) superior, (2) inferior, (3) lateral, or (4) medial. An estimate of needle length should be deter-
MAMMOGRAPHIC FEATUREANALYSIS
229
mined by measuring the distance from skin surface to target. Most localization systems are available in a variety of lengths to accommodate most lengths encountered in actual practice. On the day of localization, after a thorough explanation of the procedure to the patient, the point of insertion is marked on the skin representing the shortest distance to the target. The skin mark is made after appropriate films with a localization compression paddle. The localization device should be inserted directly through and below the target. The latter is verified by an orthogonal view. To ensure a perpendicular approach to the target, the localizing light should be used. It will cast a shadow of the needle hub on the skin, and when the shadow of the needle hub obscures the shadow of the needle shaft, a perpendicular approach is ensured. All breast tissue that was removed secondary to a localization procedure must be radiographed. This procedure will determine if the target as well as the entire localization device has been successfully removed. This information must be conveyed to the surgeon in the operating suite. If localization is unsuccessful, an additional specimen may be obtained. If still
unsuccessful, a postlocalization film must be ordered to revisualize the target and if necessary, plan for a second localization. For specimens containing microcalcifications, radiographs of the sliced specimen are also obtained, and the areas containing these microcalcifications are marked for pathology. The final task is to verify that the localized target was actually seen by the pathologist. This is accomplished either by periodic visits with the pathologist or by periodic review of their reports. This assumes greatest importance with calcifications. If microcalcifications are not mentioned in a pathology report for which microcalcifications were the target and successfully removed, a radiograph of the pathological block or use of polarized light may be required. 4s,49 One should also realize that it is possible to lose some calcification during pathological processing. Although this has not represented complete loss of calcification removed, the potential does exist for this event to occur. 5~ ACKNOWLEDGMENT
The authors wish to thank Dr. Laura Perry for the line drawings contained in the article.
REFERENCES
1. Salomon A: Beitrage zur pathologie und klinik der mammakarzinome. Arch Klin Chir 101:573-668, 1913 2. American Cancer Society: Cancer Facts and Figures-1992. Atlanta, GA, American Cancer Society. 3. Boring CC, Squires TS, Tong T: Cancer statistics 1992. CA Cancer J Clin 42:19-38, 1992 4. Shapiro S, Strax P, Venet L: Periodic breast cancer screening in reducing mortality from breast cancer. JAMA 215:1777-1785, 1971 5. Tabar L, Fagerberg G, Gad A, et al: Reduction in mortality from breast cancer after mass screening with mammography. Randomized trial from the breast cancer screening working group of the Swedish National Board of Health and Welfare. Lancet 1:829-832, 1985 6. Roberts MM, Alexander FE, Anderson TJ, et al: Edinburgh trial of screening for breast cancer: Mortality at 7 years. Lancet 335:241-246, 1990 7. Miller AB, Baines CJ, To T, et al: Canadian National Breast Screening Study: I. Breast cancer detection and death rates among women aged 40 to 49 years. Can Med Assoc J 147:1459-1476, 1992 8. Miller AB, Baines CJ, To T, et al: Canadian National Breast Screening Study: II. Breast cancer detection and death rates among women aged 50 to 59 years. Can Med Assoc J 147:1477-1488, 1992
9. Baines CJ, Miller AB, Kopans DB, et al: Canadian National Breast Screening Study: Assessment of technical quality by external review. AJR 155:743-747, 1990 10. Tabar L, Fagerberg G, Duffy SW, et al: The Swedish two-county trial of mammographic screening for breast cancer: Recent results and calculation of benefit. J Epidemiol Comm Health 43:107-114, 1989 11. Eklund GW, Busby RC, Miller S, et al: Improved imaging of the augmented breast. A JR 151:469-473, 1988 12. Jackson VP, Dines KA, Bassett LW, et al: Diagnostic importance of the radiographic density of noncalcified breast masses: Analysis of 91 lesions. AJR 157:25-28, 1991 13. Hermann G, Keller RJ, Halton K, et al: Nonpalpable ductal carcinoma in situ versus infiltrating carcinoma of the breast--Can they be differentiated by mammography? J Can Assoc Radiol 42:219-222, 1991 14. Stomper PC, Leibowich S, Meyer JE: The prevalence and distribution of well-circumscribed nodules in screening mamnaography: Analysis of 1500 mammograms. Breast Dis 4:197-203, 1991 15. Meyer JE, Kopans DB, Lawrence WD: Normal intramammary lymph nodes presenting as occult breast masses. Breast 40:30-32, 1982 16. Egan RL, McSweeney MB: Intramammary lymph nodes. Cancer 51:1838-1842, 1983
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17. Kopans DB, Swarm CA, White G, et al: Asymmetric breast tissue. Radiology 171:639-643, 1989 18. Homer MJ, Smith TJ: Asymmetric breast tissue. Radiology 173:577-578, 1989 (letter to editor) 19. Kopans DB: Asymmetricbreast tissue: Reply. Radiology 173:577-578, 1989 (letter to editor) 20. Stomper PC, Davis SP, Weidner N, et al: Clinically occult, noncalcified breast cancer: Serial radiologic-pathologic correlation in 27 cases. Radiology 169:621-626, 1988 21. Bassett LW, Gold RH, Cove HC: Mammographic spectrum of traumatic fat necrosis: The fallibility of "pathognomonic" signs of carcinoma. AJR 130:119-122, 1978 22. Gold RH, Montgomery CK, Rambo ON: Significance of margination of benign and malignant infiltrative mammary lesions: Roentgenographie-pathological correlation. AIR 118:881-894, 1973 23. Sickles EA, Herzog KA: lntramammary scar tissue: A mimic of the mammographic appearance of carcinoma. AIR 135:349-352, 1980 24. Sickles EA, Herzog KA: Mammography of the postsurgical breast. AJR 136:585-588, 1981 25. Evers K, Troupin RH: Lipid cyst: Classic and atypical appearances. AJR 157:271-273, 1991 26. Leborgne R: Diagnosis of tumors of the breast by simple roentgenography: Calcifications in carcinoma. AJR 65:1-11, 1951 27. Kopans DB, Meyer JE, Homer M J, et al: Dermal deposits mistaken for breast calcifications. Radiology 149: 592-594, 1983 28. Homer M J, Marchant D J, Smith TJ: The geographic cluster of microcalcifications of the breast. Surg Gynecol Obstet 161:532-534, 1985 29. Berkowitz JE, Gatewood OMB, Donovan GB, et al: Dermal breast calcifications: Localization with templateguided placement of skin marker. Radiology 163:282, 1987 30. Homer M J, Cooper AG, Pile-Spellman ER: Milk of calcium in breast microcysts: Manifestation as a solitary focal disease. A JR 150:789-790, 1988 31. Linden SS, Sickles EA: Sedimented calcium in benign breast cysts: The full spectrum of mammographic presentations. AJR 152:967-971, 1989 32. Stacey-Clear A, McCarthy KA, Hall DA, et al: Calcified suture material in the breast after radiation therapy. Radiology 183:207-208, 1992 33. Stigers KB, King JG, Davey DD, et al: Abnormalities of the breast caused by biopsy: Spectrum of mammographic findings. AJR 156:287-291, 1991 34. Ciatto S, Catarzi S, Morrone D, et al: The differential
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diagnostic criteria of breast microcalcifications. Radiol Med 83:390-394, 1992 35. Stomper PC, Connolly JL: Ductal carcinoma in situ of the breast: Correlation between mammographic calcification and tumor subtype. AJR 159:483-485, 1992 36. Roses DF, Mitnick J, Harris MN, et al: The risk of carcinoma in wire localization biopsies for mammographically detected clustered microcalcifications. Surgery 110:877886, 1991 37. Peters ME, Fagerholm MI, Scanlan KA, et al: Mammographic evaluation of the postsurgical and irradiated breast. Radiographics 8:873-899, 1988 38. Berkowitz JE, Gatewood OMB, Goldblum LE, et al: Hormonal replacement therapy: Mammographic manifestations. Radiology 174:199-201, 1990 39. Adler OB, Engel A: Invasive lobular carcinomaMammographic pattern. ROFO 152:460-462, 1990 40. Ikeda DM, Andersson I, Wattsgard C, et al: Interval carcinomas in the Malmo mammographic screening trial: Radiographic appearance and prognostic considerations. AJR 159:287-294, 1992 41. Sickles EA: Periodic mammographic follow-up of probably benign lesions: Results in 3,184 consecutive cases. Radiology 179:463-468, 1991 42. Varas X, Leborgne F, Leborgne JH: Nonpalpable, probably benign lesions: Role of follow-up mammography. Radiology 184:409-414, 1992 43. D'Orsi CJ: To follow or not to follow, that is the question. Radiology 184:306, 1992 (editorial) 44. Kopans DB: The positive predictive value of mammography. AIR 158:521-526, 1992 45. Gallagher WJ, Cardenosa G, Rubens JR, et al: Minimal-volume excision of nonpalpable breast lesions. AIR 153:957-961, 1989 46. Homer M J: Localization of nonpalpable breast lesions: Technical aspects and analysis of 80 cases. AJR 140:807-811, 1983 47. Sickles EA: Imaging insights: Breast calcifications-Parenchymal or dermal? Radiology 178:588, 1991 48. Rebner M, Helvie MA, Pennes DR, et al: Paraffin tissue block radiography: Adjunct to breast specimen radiography. Radiology 173:695-696, 1989 49. D'Orsi CJ, Reale FR, Davis MA, et al: Is calcium oxalate an adequate explanation for nonvisualization of breast specimen calcifications? Radiology 182:801-803, 1992 50. D'Orsi CJ, Reale FR, Davis MA, et al: Breast specimen microcalcifications: Radiographic validation and pathologic-radiologic correlation. Radiology 180:397-401, 1991
DR. Albert Salmon first reported on I Nthe1913,effectiveness of radiographic technique as applied to mastectomy specimens to demonstrate differences in the margins of invasive and circumscribed breast carcinoma. 1 Eighty years later, skepticism from some of our clinical and epidemiological colleagues concerning the efficacy of mammography persists. Often this attitude is fostered by a lack of knowledge of the goals and limitations of mammography as well as by the multifaceted problems of breast cancer in our society. With the realization that one out of nine American women will develop breast cancer in their lifetime2 and that breast cancer is the second leading cause of cancer mortality,3 attention has been directed toward mammography as the best means of detecting preclinical breast malignancy. This concept has been repeatedly justified in randomized screening trials.4-6 The importance of quality assurance in any mammography-based screening program has developed in a parallel manner as substantiated by the Canadian National Breast Cancer Screening Study7,s and critiques of their technique. 9 Currently the best available mechanism for obtaining high-quality mammography is referral of women to facilities where the mammographic equipment is accredited by the American College of Radiology. Passage of the Federal Mammography Quality Standards Act of 1992 and establishment of a panel by the Agency for Health Care Policy and Research to determine
ABBREVIATIONS BIRADS, Breast Image Reporting and Data System; CC, craniocaudal; DCIS, ductal carcinoma in situ; MLO, mediolateral-oblique.
From the Department of Radiology, Universityof Massachusetts Medical Center, Worcester, MA; and the Department of Radiology, Harvard Medical School, Boston, MA. Address reprint requests to Carl Z D'Orsi, MD, Professor, Department of Radiology, Universityof Massachusetts Medical Center, 55 Lake Ave North, Worcester, MA 01655. Copyright 9 1993 by W.B. Saunders Company 0037-198X/93/2803-000555.00/0 204
quality standards for mammography reinforce the interest in mammography not only from a medical standpoint but from social and legislative perspectives as well. The orientation of this communication differs from other articles on mammography. Ordinarily, findings for malignant and benign conditions are presented using the various pathological entities to introduce and describe associated mammographic findings. However, in daily medical practice mammographic findings and details of their features ultimately guide the recommendations and outcome whereas the actual pathology assumes a secondary yet still important status. This article is divided into sections on technique, masses, calcifications and associated findings, new and/or developing findings, recommendations, and localization. Findings and their definitions are those recommended by the newly established American College of Radiology Breast Imaging Reporting and Data System (BIRADS). They are illustrated by line drawings alone, both line drawings and mammographic examples, or solely by mammograms. Each section on mammographic features attempts to discriminate relatively benign from malignant features. The ultimate decision to obtain tissue, short-term follow-up, or other imaging procedures (such as ultrasound) must be based on a clear understanding of mammographic findings and experience. Asymptomatic women and those with signs or symptoms related to the breast can benefit from breast-imaging studies. The major role for mammography is the early detection of breast cancer in asymptomatic women. The efficacy of screening has been established by randomized trials in which absolute mortality has been reduced. Although mammography can detect the majority of breast cancers, some lesions may elude mammographic detection and yet be palpable. Thus an important component of screening is the physical examination provided by the referring physician or the screening facility. Mammographic screening involves the performance of standard projections, usually the meSeminars in Roentgenology, Vol XXVIII, No 3 (July), 1993: pp 204-230
Fig 1. Compression effect. CC view (A) demonstrates a focal density (arrow}, which loses its mass-like appearance w i t h a compression view (B).
Fig 2.
Round and oval mass. Line drawing of round (A) and oval (B) mass. Fibrodenoma.
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D'ORSI AND KOPANS
diolateral-oblique (MLO) and craniocaudad (CC) views. 1~ In some settings, additional images are undertaken immediately to solve a question, and in other settings, the patient is recalled for further evaluation. Mammography may be coupled with other breast-imaging techniques (such as ultrasound) for evaluation of women with a sign or symptom suggesting cancer. Although this diagnostic mammogram may not influence clinical care, the study is still important to evaluate the clinical lesion as well as to screen the remaining ipsilateral and contralateral breast. Just as clinical decisions may be made solely on mammographic suspicions, the negative mammogram in the setting of a clinical abnormality must not deter or delay management. TECHNIQUE
Earlier detection of breast cancer using mammography requires a well-organized and systematic examination. High-quality imaging requires accredited, dedicated mammography equipment that is carefully maintained with appropriate quality controls. The technologist performing the examination must be well trained and skilled in proper positioning. Appropriate exposures are required using low-kilovolt (peak) techniques. The film processor should be optimized for mammographic film, and the quality control program should be carefully tailored to maintain optimum film development. A detailed description of these parameters can be Fig 4. Irregular mass. Medial oblique (A) and magnification compression-spot view (B) demonstrate an irregular mass with angular protrusions. Note benign, round calcifications within the mass. Infiltrating ductal carcinoma.
Fig 3. Lobulated mass. Lobes (arrows) from well-circumscribed mass. Fibroadenoma.
obtained from the American College of Radiology. Mammograms should be read on view boxes that arc masked to exclude extraneous light and glare from around the images. The breasts should be considered symmetrical organs, and the mammograms should be positioned on the view box to take advantage of this symmetry in a search for asymmetry. Position mammograms in the same orientation at all times so that left-right confusion is minimized. Once an abnormality has been detected, it
MAMMOGRAPHIC FEATURE ANALYSIS
Fig 5. Circumscribed. Sharp definition between margin and surrounding tissue.
must be properly characterized by careful analysis of its mammographic features. Various mammographic maneuvers allow one to determine the three-dimensional findings. This initial step is important because numerous overlapping structures in the breast form normal summation shadows that can mimic true abnormalities.
Fig 6. Microlobulated margin. Line drawing (A) of irregularity of the margin raising the possibility of invasion, Magnified compression-spot view (B) of microlobulated margin (arrows). Invasive intraductal carcinoma.
207
The two main radiographic maneuvers to aid in detection and characterization are different views and/or obliquities and tailored compression. Our first task is to verify a finding, considering that the breast presents an ideal background both to create and camouflage findings. The 90~ view, exaggerated axillarycraniocaudal view, roll view, and spot-compression view are extremely useful toward this end. The task is to differentiate adjacent tissues from each other by changing their relationship. In summation shadows caused by overlapping glandular tissue, varied views allow a confident appraisal of such densities. In the case of true findings, little change in appearance occurs with these views. The magnification spot-compression view allows a more critical analysis of the margin of a mass and the morphology of calcific elements. If a palpable mass is present, a tangential view, placing the mass in profile, will often delineate and/or enhance the margins. These mammographic maneuvers are used to
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both verify and characterize mammographic findings. The implant-displaced technique pioneered by Ecklund 11 allows the technologist to posteriorly displace the implant with a compression paddle while simultaneously pulling breast tissue on the film cassette. This maneuver delineates more breast tissue in an optimal manner. However, at the same time no maneuver with
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the implanted breast will allow as much tissue visualization as the breast without implants. MASSES
Because the breast is composed of glandular and fatty tissue in random distributions, false projection of what appears to be a mass is a possibility. This appearance is termed a summation artifact and is often resolved by the use of
Fig 7. Obscured margin. Line drawing (A) highlights absence of a margin owing to adjacent glandular tissue. This may be considered a mammographic "silhouette" sign. The obscuration is suggested on the mass observed in the medial oblique view (B) (arrow) and emphasized on the magnification compression-spot view (C), demonstrating glandular tissue (short arrows) obscuring the margin that is well-observed in an adjacent area (large arrow). Similar findings on a second case (D) show glandular tissue (large aYrows) obscuring a portion of the margin (small arrows).
MAMMOGRAPHIC FEATURE ANALYSIS
orthogonal and spot-compression views (Fig 1). A true mass is a space-occupying lesion persisting in two different projections after appropriate evaluation is completed. A possible mass observed in only a single projection should be called a density until its three dimensions are confirmed. In order to successfully recommend appropriate management, several features of the mass should be evaluated. A description of the shape, margin, and density allow an orga-
!ii!iiii!!i!:i~< 84184 ~
Fig 8. Indistinct margin. CC v i e w (A) demonstrating mass with almost completely circumscribed margin. However, magnification spot-compression v i e w (B) shows an indistinct margin (arrow) with no adjacent glandular tissue, Secretory carcinoma.
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nized analysis and recommendation. With standardized language, an analysis is understandable to both clinician and radiologist. The shape of a mass may be categorized as round, oval, lobulated, or irregular. The round mass is spherical or globular and the oval mass is elliptical (Fig 2). The lobulated mass (Fig 3) has contours with undulations that may indicate a degree of autonomy. Finally the irregular mass (Fig 4) is one whose shape cannot be described
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by any of those ~previously defined. The latter indicates the most worrisome situation as far as shape analysis is concerned. The margin characteristics of a mass observed mammographicaily are the major determinants of its benign or malignant status. The circumscribed (well-defined or sharply defined) mass is one whose margins are sharply demarcated with an abrupt transition between the lesion and surrounding tissue. Without additional modifiers, nothing in this appearance suggests infiltration (Fig 5). A microlobulated margin has an edge that undulates with short cycles and may indicate microscopic invasion of surrounding breast tissue (Fig 6). Obscured margins are hidden by superimposed or adjacent normal tissue and cannot be assessed any further (Fig 7), and an indistinct margin indicates that poor definition of the edge is not likely due to superimposed breast tissue and thus raises the concern of infiltration by malignancy (Fig 8). Finally, a mass with fine lines radiating from its margins is said to be spiculated and is the most suspicious margin feature for malignancy (Fig 9).
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Fig 10. Fat-containing mass. Lucent mass (arrow) with thin wall in an area of previous surgery. This is most compatible with a traumatic lipid cyst,
The density of a mass is probably most difficult to accurately a c c e s s . 12,13 Although singularly it may not be a powerful discriminator between benign and malignant, taken with other
Fig 9. Spiculated margin. Medial oblique view (A) demonstrating mass (arrow) with spiculations. The magnification spotcompression view (B) more clearly demonstrates the fine nature and radial orientation of spiculations (small arrows). Invasive ductal carcinoma.
MAMMOGRAPHIC FEATURE ANALYSIS
features of a mass, the density assessment can be extremely useful. The X-ray attenuation of a mass is related to the attenuation of an equal volume of fibroglandular breast tissue. Breast cancers are most often of equal or higher density than glandular elements. Thus a highdensity mass is one that is conspicuous owing to increased radiographic attenuation, and a lowdensity mass is conspicuous for diminished attenuation compared with approximately equal volumes of glandular tissue. The equal or isodense
Fig 11. Dilated duct. There is a tubular density in the left CC view from 1989 (A) (arrow). There are no clinical or associated mammographic features to imply malignancy. A similar view on a follow-up examination in 1990 (B) does not demonstrate the tubular structure.
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mass is approximately equal in attenuation to surrounding glandular elements. Of special interest is the fat-containing or radiolucent mass. This category includes all lesions containing fat, such as lipid cysts, lipomas, and galactoceles as well as mixed lesions, such as hamartomas (Fig 10). Because there are no reported examples of fat-containing breast malignancies, the importance of this finding is obvious. Several special cases cannot be strictly catego-
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Fig 12. Intramammary lymph node. Lobulated, circumscribed mass with central lucency (arrow).
rized with masses. The tubular density most likely represents an enlarged duct. If unassociated with other suspicious clinical or mammographic findings, a tubular density usually has minor significance (Fig 11). Intramammary lymph nodes are typically reniform, have a radiolucent notch due to fat at the hilum, and are generally 1 cm or less in size. They may be larger than 1 cm when fat replacement is pronounced. Multiplicity or marked fat replacement may cause a single lymph node to resemble several rounded masses. This specific diagnosis should be reserved for masses in the axillary and superior portion of the breast, although on rare occa-
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sions they may occur in other areas of the breast (Fig 12). 14-16 Asymmetric breast tissue is judged relative to the corresponding area in the contralateral breast and includes a greater volume or density of breast tissue and ducts. The area frequently assumes different shapes on orthogonal views. This usually represents a normal variation but may have greater significance if it corresponds to a clinical finding (Fig 13)) 7-19Focal asymmetric tissue cannot be accurately described using the previously described shapes. Although asymmetric, these lesions may be observed on two views with a similar shape but not as conspicuous as a true mass and lacking the defined margins of a mass. Focal asymmetric tissue may represent an island of normal breast tissue, but its lack of specific benign characteristics may warrant further evaluation. Additional imaging may show a true mass or other significant features. Architectural distortion includes spiculation radiating from a point with no definite mass visible (Fig 14). This appearance can also include focal retraction or distortion of the edge of the breast parenchyma. Architectural distortion may also be associated with a mass.
Differential Considerations for Masses Although listing all the possible combinations of shape, margin, density, and special cases and their significance is not practical, several examples are presented here to demonstrate how mass-feature analyses can significantly contribute to formulate pertinent management options. The round or oval, well-circumscribed mass of equal or low density a n d / o r fatcontaining mass has all the criteria of a benign mass. An irregular mass with spiculated margins
Fig 13. Asymmetric breast tissue. Line drawing of nonfocal asymmetry (highlighted area) displaying different shape between the CC and MLO views.
MAMMOGRAPHIC FEATURE ANALYSIS
213
Fig 14. Architectural distortion. Line drawing (A), CC view (B), and medial oblique view (C) demonstrate the area of distortion (large arrows) (B and C) with fine radiating lines converging to a single region with no mass formation (small arrows) {B). Invasive ductal carcinoma.
or an area of architectural distortion has significant criteria for malignancy. 2~ At the same time, an important caveat must be added with architectural distortion and to a
Fig 15. Architectural distortion. CC (A) and MLO view (B) depicting distorted anatomy and fine spiculation (small arrows) unassociated with a mass. Note the lucent area (large arrow) centrally placed within the distortion secondary to fat necrosis. Prior surgical biopsy.
lesser extent with spiculated masses. Intramammary scar tissue a n d / o r fat necrosis from surgical or nonsurgical trauma may mimic the architectural distortion associated with malignancy
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D'ORSI AND KOPANS Table 1. Malignant Potential. Mass Feature Analysis Features
Shape Round Oval Lobular Irregular Margins Circumscribed Microlobulated Obscured Indistinct Spiculated Density High Equal Low Fat containing Special Cases Solitary dilated duct Intramammary lymph node Asymmetric breast tissue Focal asymmetric density Architectural distortion
Benign/ Indeter- Suspicious/ Probably Benign minate Highly Suspicious X X X X X X X X
X X X
X X X
X
X X X
X X X
Fig 17. Early vascular calcification. Heterogeneous elements of calcification with a straight tubular distribution (arrows). Although these calcifications do not definitely demonstrate parallel tracks of calcification, their tubular arrangement and long linear course suggest vascular calcification.
(Fig 15). Although the breast often heals with little mammographically visible abnormality after a biopsy, with the increased use of biopsy for nonpalpable findings as well as conservative therapy for early breast carcinoma, we can expect postsurgical or traumatic architectural distortion to increase. 21,22
Fig 16. Dermal calcifications. Rim calcification (arrows) located adjacent to the inferior, posterior skin margin. This represents a typical appearance and location for dermal calcification.
Fig 18. Popcorn calcification. Extremely coarse calcifications often occupying all of an involuted fibroadenoma.
MAMMOGRAPHIC FEATURE ANALYSIS
215
a biopsy siteY Table 1 lists mass features and their malignant potential. CALCIFICATIONS
Mammography is the only examination that can consistently identify calcification within the breast, which can signify early malignancy. Leborgne 26 described calcification in terms still in current use. When reporting on calcification it is important to describe the morphology of each element of calcification as well as their distribution within the breast. Certain calcifications are almost always benign whereas others are of intermediate and great concern. Distribution modifiers also require assessment.
Typically Benign Calcification
Fig 19.
Large rod-like calcifications. Numerous coarse lin-
ear calcifications (arrow) oriented toward the nipple,
Architectural distortion from malignant and nonmalignant causes is virtually indistinguishable. A baseline mammogram 2 to 3 months after surgery on the involved side may preclude the need to rebiopsy. 23,24A round, lucent area situated in an area of architectural distortion after surgical intervention may allow a more confident diagnosis of traumatic lipid cyst within
Calcification does not always need to be noted in the mammography report but should always be reported when the radiologist is concerned that it might be misinterpreted by other observers. Skin calcifications are typically lucent-centered deposits around the areola, axillary or medial, and inframammary portions of the breast. When in these locations with lucent centers, they are pathognomonic (Fig 16). Calcification with atypical elements and/or locations may be confirmed as dermal by tangential views. 27-29 Vascular calcifications occur as parallel tracks or linear tubular calcifications that are clearly associated with blood vessels. Difficulty may arise in characterization during the initial phases of vessel calcification. Magnification views and
Fig 20. Round/punctate calcifications. Round (A) and punctate (B) calcifications distributed in a diffuse manner. The morphology of the elements is similar and differs only in size.
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D'ORSI AND KOPANS
films with slightly different obliquities are often helpful (Fig 17). Fibroadenomas, as part of involution, frequently calcify with a coarse or popcorn appearance (Fig 18). However, initial calcification may be finer and difficult to distinguish from those caused by cancer. Large rod-like calcifications are benign. These calcifications form continuous rods that are
Fig 21. Lucent-centered calcifications. Fairly thick rim (arrow) with lucent center.
Fig 22. Rim (eggshell) calcifications. These are benign forms of calcification often occurring in cyst walls, Magnified view of rim calcifications.
Fig 23. Milk of calcium, MLO view (A) with oval mass and partially obscured margins (large arrow), Small area of slightly increased density projected within the mass (small arrow), Ninety-degree lateral view (B) again demonstrating mass (large arrows). Linear ca|cific density (small arrow) representing movable calcific particles within large cyst.
MAMMOGRAPHIC FEATURE ANALYSIS
occasionally branching and usually 1 mm or more in diameter. They may have lucent centers if the calcium surrounds rather than fills the ectatic duct or if the intraductal debris is incom-
217
pletely calcified. This is the type of calcification found in secretory disease and duct ectasia (Fig 19). Round calcifications may vary in size and are
Fig 24. Suture calcification. Line drawing of retained, unabsorbed suture material (A). MLO view with linear arrangement of calcified suture material.
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D'ORSI AND KOPANS
usually considered benign. When under 1 ram, they are frequently formed in the acini of lobules. When under 0.5 mm, the termpunctate may be used (Fig 20). Spherical or lucent-centered calcium deposits may range in size from under 1 mm to over 1 cm or more. They are smooth and round or oval
Fig 26. Amorphous calcification. Magnified views (A and B) of t w o separate clusters of indistinct calcifications. These forms are often at the limit of visibility owing to their diminished density. Both areas were removed and were benign without pathological risk factor for malignancy.
Fig 25, Dystrophic calcification. Coarse, irregular calcification posteriorly and inferiorly placed. Patient with a transverse rectus abdominis myocutaneous flap reconstruction.
with a lucent center. These deposits often develop in areas of fat necrosis, within ectatic ducts, and occasionally in the early phase of degenerating fibroadenoma (Fig 21). When the wall of these lucent-centered calcifications is thin, usually well under 1 mm, the term rim or eggshell calcification may be used (Fig 22). Calcification in the wall of cysts are the most common cause of rim calcification.
MAMMOGRAPHIC FEATURE ANALYSIS
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The varying appearance of calcifications on different mammographic projections is typical for milk of calcium. On the CC image, they are often less evident and appear as fuzzy deposits, yet on the horizontal beam-lateral they are sharply defined with a semilunar, crescent, or linear configuration. This appearance is compatible with sedimented calcification within cysts that defines the dependent portion (Fig 23). 30'31 Suture calcifications are the consequence of calcium deposition on suture material and are relatively common in the breast treated conservatively for breast cancer. They are typically linear or tubular in appearance, and knots are frequently visible (Fig 24). 32 Dystrophic elements usually develop after trauma or irradiation. Although irregular in shape, they are usually over 0.5 mm in size and often have lucent centers (Fig 25). 33
Calcifications of Intermediate and Great Concern These calcific elements range from those that are probably benign to those highly suggestive of malignancy. After mammographic evaluation, they frequently require further characterization in the form of follow-up or biopsy. Amorphous or ind&tinct elements are often round or flake-shaped calcifications that are sufficiently small or hazy in appearance that a more specific classification is impossible (Figs 26 and 27). Pleomorphic or heterogeneous granular calcification may have a morphology similar to the amorphous forms but is denser and more conspicuous. The forms are irregular with varying sizes and shapes and are usually less than 0.5 mm in size (Fig 28). Fine and/or branching linear (casting) calcifications are thin, irregular calcifications that appear linear but are discontinuous and under 0.5 mm in width. Their appearance suggests luminal filling of a duct involved irregularly by breast cancer (Fig 29).
Distribution Modifiers Not only is calcific-element morphology important but the arrangement of the calcific elements may provide clues for further management. Grouped or clustered calcifications occupy a relatively small volume (less than 2 cc) of breast tissue (Fig 30). Linear calcifications are arrayed in a line with or without branch points
Fig 27. Architectural distortion and amorphous calcification. There is focal retraction at the edge of the breast parenchyma (A) (arrow). Magnification compression-spot view (B) enhances the architectural distortion (curved arrow) and also demonstrates a cluster of amorphous calcifications (straight arrows), Invasive ductal carcinoma,
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Fig 28. Pleomorphic-heterogenous calcification. These are similar in appearance to the amorphous forms but are much denser and more conspicuous. Line drawing (A) and magnified view (B) (arrow) of typical appearance. The morphology, clustered distribution, and large numbers of caicific elements (B) strongly suggest malignancy. Moderately differentiated invasive ductal carcinoma.
A
Fig 29. Fine and/or branching linear (casting) calcification. Line drawing (A) and magnified image {B) (arrow) show thin, irregular linear branching elements arranged in a cluster. Specimen radiograph (C) (arrow) depicts calcific morphology to better advantage. Invasive ductal carcinoma and DCIS.
Fig 30. Clustered calcifications. Heterogeneous calcifications are distributed in a small volume of tissue (large arrows). Note the coarse (popcorn) calcification (curved arrow). Involuted fibroadenoma and intraductal hyperplasia.
Fig 31. Linear distribution. Heterogeneous calcification (A) (arrows) is oriented in a linear manner over a short distance and does not conform with a tubular density. Multiple foci of intraductal carcinoma, comedo type. Punctate and heterogeneous calcifications (B) (arrows) are distributed in a branched linear pattern. Intraductal carcinoma.
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Fig 32. Segmental distribution. Distribution is not as confined as clustered or linear patterns and suggests involvement of more than one ductal system.
(Fig 31). This appearance increases concern because the arrangement suggests a ductal origin. A variation of the linear distribution is segmental, which suggests deposits in multiple ducts and their branches and raises the possibility of multifocal malignancy. Although benign causes of a segmental arrangement exist, such as secretory disease, this distribution should provoke greater concern when the morphology of the calcific elements is not specifically benign (Fig 32). Calcifications prevalent in a large volume of breast tissue not necessarily conforming to a duct distribution but not affecting all areas of the breast are regional in distribution (Fig 33). Diffuse or scattered calcifications are distributed randomly throughout the breast (Fig 34). Multiple groups of calcifications indicate more than
Fig 33. Regional distribution. This pattern is more extensive than a segmental distribution but not as disseminated as a diffuse distribution.
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Fig 34. Diffuse/scattered distribution. The calcific elements in this pattern are randomly distributed.
one group of elements similar in morphology and distribution (Fig 35). Multifocal areas of malignancy presenting as identical groups of calcification occur infrequently. However, we must assure that the element anatomy is not suspicious and that all groups are similar in appearance.
Differential Considerations for Calcification Once analysis and description of microcalcification and its distribution is accomplished, the much more difficult task of management begins. We have tried to differentiate management on the basis of benign or malignant potential. An excellent source of material to gain confidence in this endeavor is one's own biopsy material. Review of cases with assignment of an estimate of malignant potential (1 for benign, 5 for malignant) allows for a semiquantitative score
Fig 35. Multiple groups. Calcifications of similar element shape and distribution indicate similar pathology. Multiple clusters of round calcifications are depicted in the line drawing.
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Table 2. Malignant Potential. Calcification Feature Analysis Features
Elements Typically benign Amorphous Heterogeneous Linear/branching Distribution Cluster Linear Segmental Regional Scattered/diffused Multiple groups
Benign/ Indeter- Suspicious/ Probably Benign minate Highly Suspicious
X
ASSOCIATED FINDINGS X
X X X X X
strates features of calcifications with their malignant potential.
X
of performance. This exercise will help demystify the management process and also serve as an invaluable teaching aid. Using biopsy material, Ciatto and colleagues 34 demonstrated that punctate calcifications are infrequently associated with malignancy whereas heterogeneous, fine branching linear calcification has a high predictive value for malignancy. In a double-blind study conducted by Stomper et al, 35 comedo types of ductal carcinoma in situ (DCIS) are accompanied by linear-branching calcification, and noncomedo DCIS is more often associated with heterogeneous (granular) elements. Similar information is presented by Roses et al. 36 In their study group biopsied for microcalcification, 95% had malignancy when more than 10 linear calcifications were unassociated with a mass or at least 1 linear calcification was associated with a mass. Conversely, punctate calcifications were benign. Table 2 demon-
Associated findings are usually found in conjunction with masses and/or calcifications, but they may stand alone as primary findings when no other abnormality is present. Skin and nipple retraction (Fig 36) is an abnormal tethering or pulling in of the skin or nipple. When associated with masses and/or indeterminate calcification, retraction is an ominous sign. Benign skin retraction often occurs in an area of prior biopsy. By marking visible scars on the skin of the breast, this cause of retraction can often be determined. Nipple retraction assumes importance as an isolated finding when the onset is recent. Skin thickening may be focal or diffuse. When associated with suspicious masses, calcifications, or clinical findings of inflammation, thickening indicates dermal lymphatic obstruction. Biopsy scars may also produce thickened skin. Radiation therapy, generalized edema, and inflammatory carcinoma may all produce a generalized thickening of the skin around the breast. 37 Trabecular thickening indicates enlargement of the fibrous septa of the breast and is found in many of the same conditions as diffuse skin thickening (Fig 37). Skin lesions (Fig 38) should be marked before filming the breast. They may be mentioned when projected over the breast in two views and possibly mistaken for an intramammary mass. Enlarged, nonfatty replaced
iLii
/
A Fig 36. Nipple/skin retraction. Nipple retraction assumes more importance when associated with recent onset and/or a mammographic finding (A). Skin retraction (B) is often observed after surgery with advanced breast cancers and with malignancies immediately adjacent to the skin.
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Fig 38. Skin lesion. Mention of a skin lesion may be useful if it is projected within the breast on t w o different views. Lucency that sometimes surrounds a skin lesion is probably secondary to surrounding air.
prior examination. With the increased use of estrogen-replacement therapy, nonfocal diffuse changes in glandular tissue may be observed. 38 Invasive lobular carcinoma may present as an asymmetric density with none of the typical
Fig 37. Skin and septal thickening. Skin thickening (large arrows) with increased thickness and conspicuity of septa (small arrows) 3 months after surgery and radiation therapy.
axillary lymph nodes may be noted in the report, although mammographic assessment of these nodes is unreliable (Fig 39). NEW AND/OR DEVELOPING FINDINGS
Although difficult to categorize, new or developing changes are of utmost importance, especially for detection of early, subtle malignancy. The analysis requires comparison with prior examinations whenever possible. Of greatest concern are mammographic findings that change over a relatively short period of time and findings that are new when compared with a recent
Fig 39. Axillary nodes. Nodes that are greater than 1-1.5 cm, are without fatty replacement, and are matted, as depicted in the line drawing, are most suspicious for malignancy.
MAMMOGRAPHiC FEATURE ANALYSIS
features of malignancy. Often the only possibility for determining its malignant nature is careful comparison with prior studies (Figs 40 through 43). 39 Analysis of interval carcinomas
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(carcinomas arising in the interval between scheduled mammographic screens) from the Malmo Screening Trial reinforces the need for comparison. In slightly fewer than 50% of pa-
Fig 40. Developing density. CC view from 1991 (A) shows no definite finding suspicious for malignancy. On routine follow-up in 1992, the CC view (B) shows a subtle change (arrow), which on magnification compression-spot view (C) fails to change its appearance (arrow). Invasive Iobular carcinoma.
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Fig 41. Developing density. Mediolateral oblique view (A) from 1987 suggests an irregular mass (large arrows) and spiculation (small arrows), but this appearance may be simulated by overlapping densities. No further work-up was conducted. Patient failed to return for mammography until 1992 (B), when mammogram demonstrates progression and increased conspicuity of the irregular mass (large arrows) and spiculation (small arrows). Invasive ductal carcinoma.
tients, a change owing to subtle growth was noted when examinations taken at discovery of the interval cancer were compared with the immediately prior examination. 4~ In Sickles 41 article on mammographic follow-up, 15 of 17 malignancies were identified by interval mammographic changes with 10 of 15 found between 6 to 18 months of follow-up.
RECOMMENDATIONS
Once analysis of the findings takes place, recommendations and management decisions must be made. The American College of Radiology BIRADS system was designed to ensure that ultimate breast-imaging assessment was decision oriented. Two major categories of assessment are available.
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Fig 42. New density. The right CC view from 1989 (A) demonstrates no features indicative of malignancy and appears similar to the left CC view. In 1991 (B), the density is markedly increased in the subareolar area, which on magnification compression-spot view (C) fails to show any specific malignant features. Thus, the only clue for the presence of carcinoma is subareolar asymmetric breast tissue occurring over a 2-year interval. Infiltrating ductal carcinoma.
In the screening situation, where the only decision relates to normal or abnormal, the BIRADS system recommends routine examination or additional evaluation for patients with positive studies. When findings have been thor-
oughly investigated, a more complete recommendation is required. In a negative examination, no abnormalities or other findings are noted and the breasts are symmetric. A benign status is also negative, but the interpreter may describe a
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finding, such as typical involuting calcified fibroadenoma, multiple secretory calcifications, or fat-containing masses. The probably benign category is reserved for findings that have a high probability of being benign. These are not expected to change, but the radiologist may prefer to establish their stability by recommending an initial 6-month short-term follow-up. Data are now becoming available 42-44 on the efficacy of short-term follow-up. A suspicious abnormality has features without characteristics of breast cancer but with a definite probability of malignancy, and the radiologist has sufficient concern to urge a biopsy. The highly suggestive findings are those with a high probability of representing cancer. When conveying information either verbally or in a report, communication of the radiologist's level of concern and recommendations for future patient assessment is critical. LOCALIZATION
Fig 43. New calcifications. Magnification compressionspot view from 1989 (A) shows a single coarse, branched calcification (curved arrow). On follow-up 1 year later (B), the coarse calcification is stable (large arrow), but new fine, linear branching calcifications are present (small arrow). Ductal carcinoma in situ.
Although not completely within the scope of this article dedicated to mammographic feature analysis, it is important to outline the basic technique and principles related to localization of nonpalpable mammographic findings. All of the available localizing devices are based on the design of a hooked or curved wire placed within a needle for introduction. The choice of device is relatively unimportant as long as the target is routinely removed. Failure rates of about 5% have been reported. 45,46 Of primary concern is to ensure that the finding is not artifactual and is located within the breast. This assumes a thorough work-up of any findings before a recommendation for localization. Particular attention should be paid to calcifications adjacent to a skin surface on one or more views. If a dermal location is suspected, a tangential view should be obtained. 47 After verification and work-up of a suspicious abnormality, the plan for localization should be formulated before the day of surgery. The shortest distance to the target should be chosen as the point of entry for the localizing device. This must not include insertion directed toward the chest wall. Thus we have four choices: (1) superior, (2) inferior, (3) lateral, or (4) medial. An estimate of needle length should be deter-
MAMMOGRAPHIC FEATUREANALYSIS
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mined by measuring the distance from skin surface to target. Most localization systems are available in a variety of lengths to accommodate most lengths encountered in actual practice. On the day of localization, after a thorough explanation of the procedure to the patient, the point of insertion is marked on the skin representing the shortest distance to the target. The skin mark is made after appropriate films with a localization compression paddle. The localization device should be inserted directly through and below the target. The latter is verified by an orthogonal view. To ensure a perpendicular approach to the target, the localizing light should be used. It will cast a shadow of the needle hub on the skin, and when the shadow of the needle hub obscures the shadow of the needle shaft, a perpendicular approach is ensured. All breast tissue that was removed secondary to a localization procedure must be radiographed. This procedure will determine if the target as well as the entire localization device has been successfully removed. This information must be conveyed to the surgeon in the operating suite. If localization is unsuccessful, an additional specimen may be obtained. If still
unsuccessful, a postlocalization film must be ordered to revisualize the target and if necessary, plan for a second localization. For specimens containing microcalcifications, radiographs of the sliced specimen are also obtained, and the areas containing these microcalcifications are marked for pathology. The final task is to verify that the localized target was actually seen by the pathologist. This is accomplished either by periodic visits with the pathologist or by periodic review of their reports. This assumes greatest importance with calcifications. If microcalcifications are not mentioned in a pathology report for which microcalcifications were the target and successfully removed, a radiograph of the pathological block or use of polarized light may be required. 4s,49 One should also realize that it is possible to lose some calcification during pathological processing. Although this has not represented complete loss of calcification removed, the potential does exist for this event to occur. 5~ ACKNOWLEDGMENT
The authors wish to thank Dr. Laura Perry for the line drawings contained in the article.
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