Interventional breast sonography

European Journal of Radiology 42 (2002) 17 – 31 www.elsevier.com/locate/ejrad

Interventional breast sonography Bruno D. Fornage a,*, Nour Sneige b, Beth S. Edeiken a a

Department of Diagnostic Radiology, The Uni6ersity of Texas M. D. Anderson Cancer Center, Box 57, 1515 Holcombe Boule6ard, Houston, TX 77030, USA b Department of Pathology, The Uni6ersity of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boule6ard, Houston, TX 77030, USA Received 27 November 2001; accepted 28 November 2001

Abstract This review article covers the basic applications of and latest developments in interventional breast sonography (US). For breast masses, US has become the standard for guiding needle biopsy, whether a fine needle or a core biopsy needle is used. US has also become the preferred method for guiding insertion of various localization devices for nonpalpable masses, and US’s intraoperative use for this purpose is expanding. Recently, US has been used to monitor the placement of percutaneous ablation devices, such as radiofrequency ablation needle-electrodes, into breast masses, including carcinomas. US is not indicated for the routine evaluation of microcalcifications. However, on occasion, clusters of microcalcifications without a mass can be visualized on sonograms with sufficient clarity to undertake a US-guided core biopsy if stereotactically guided biopsy cannot be performed for technical reasons. © 2002 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Ultrasonography; Interventional ultrasonography; Intraoperative ultrasonography; Breast; Breast neoplasms; Breast cancer; Microcalcifications; Biopsy; Fine-needle aspiration; Core biopsy; Localization; Radiofrequency ablation; Metallic markers

1. Introduction With the widespread use of screening mammography, a growing number of nonpalpable breast lesions that require further characterization are being detected. It is now widely accepted that the best adjunct to mammography is sonography (US). US has the unique advantage of being the only real-time cross-sectional imaging modality and is unrivaled at demonstrating needles or other devices that are inserted percutaneously into breast masses. This article will review the recent applications of interventional breast sonography.

2. General considerations in breast US When a woman presents with an indeterminate breast mass, efforts should be made to have the physical examination, mammography, US, and —if * Corresponding author. Tel.: +1-713-794-1424; fax: + 1-713-7451153. E-mail address: [email protected] (B.D. Fornage).

needed —needle biopsy performed during a single visit to the breast center [1]. Except in very young patients, who may not need a mammographic examination, US should not be done without the benefit of a careful analysis of the mammograms. It is a good practice for the breast imager to perform a targeted physical examination before starting the US study. The US examination should be performed with stateof-the-art equipment, which includes a high-frequency linear-array transducer. The latest high-resolution transducers use the broadband technology and process received signals of frequencies up to 15 MHz. Although it has been recommended by some that the US examination be limited to the area of concern based on palpation or mammographic findings (‘targeted US examination’), scanning the entire breast does not take much longer and may yield significant additional information, such as an unsuspected malignancy or additional foci of carcinoma —especially in dense breasts —that may alter the treatment plan profoundly. In patients with a history of breast cancer, the ipsilateral axilla and internal mammary chains are systematically examined [2].

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Sonograms are obtained longitudinally, transversely, and also radially around the nipple along the anatomic orientation of the ducts, as well as antiradially. The scans must be carefully labeled. The concordance between US and mammographic findings must remain the primary concern of the breast imager, especially prior to embarking on a US-guided needle biopsy or localization. The lesion’s size, shape, and location (clock position and distance from the nipple) and the appearance of the surrounding tissues (fat versus glandular tissue) must correlate perfectly on sonograms and mammograms, allowing for minimal differences in size— less than 10%— due to mammographic magnification and slight differences in clock location— no more than 2 h — due to differences in breast positioning and compression between the two types of images. Color and power Doppler US are now standard features of mid-range and high-end ultrasound scanners. Whenever a mass is demonstrated, color (power) Doppler imaging is used to assess its vascularity. On rare occasions, the visualization of a significant vessel in the vicinity of (or within) the target lesion may alter the planned pathway of the biopsy needle. Recent technological developments in breast US include tissue harmonic imaging, which boosts the spatial and contrast resolution and has shown promising results when used in conjunction with ultrasound contrast agents [3]. Three-dimensional US is not yet widely available but is expected to change the way breast sonograms are acquired, displayed, and interpreted in the not-too-distant future. The expectation is that threedimensional US will allow better assessment of the relationship between a lesion and the surrounding tissues and will facilitate the display of biopsy needles and other devices inserted percutaneously into the breast under US guidance, especially for novice operators [4].

3. US-guided needle biopsy of nonpalpable breast masses Advantages of percutaneous needle biopsy over open surgical biopsy include significant cost savings and the absence of a residual scar that might impair the interpretation of subsequent diagnostic imaging. Therefore, the procedure can be repeated as often as needed. The goal of imaging-guided percutaneous needle biopsy is to obtain a 100% reliable tissue diagnosis of nonpalpable breast lesions and thereby to reduce the number of open biopsies and the cost of diagnosing breast carcinoma [5]. Virtually any nonpalpable breast lesion that is clearly seen on sonograms can be sampled with a needle under US guidance. Both fine-needle aspiration biopsy (FNA) and core-needle biopsy (CNB) are effectively guided by real-time US.

US-guided needle biopsy is not without difficulty, and experience in every step is needed to yield optimal results. The success of US-guided biopsy of the breast depends on (a) the operator’s skills in hitting the target lesion; (b) successful tissue extraction (which depends on the operator’s technique and the nature of the tumor); (c) adequate preparation of the specimens; and (d) interpretation by an expert pathologist (or cytopathologist). Any factor compromising the success of any step jeopardizes the success of the procedure. US-guided needle biopsy must be performed after a meticulous review of recent mammograms to ensure that the sonographic lesion to be biopsied correlates, without a doubt, with the lesion in question on mammograms. This obviously does not apply to lesions seen on US alone. US-guided interventional procedures must be performed after all imaging has been completed to avoid the risk of misinterpreting a post-biopsy hematoma on subsequent imaging [6,7].

3.1. FNA 3.1.1. Equipment and technique At M. D. Anderson Cancer Center, we have been using a 1.5-inch (3.8-cm) 20-gauge hypodermic needle for FNA of breast lesions. Rarely, a 2-inch (5-cm) 21-gauge needle is needed because the lesion is deep and/or the breast is large. If a needle guide attached to the probe is used, a longer needle (e.g. a spinal needle) must be used to compensate for the longer needle pathway through the guide. Thinner needles are flexible and may deviate from their expected course, making their visualization more difficult, and often provide insufficient specimens from solid lesions, necessitating multiple passes. In contrast, a single pass with a 20gauge needle is usually sufficient to provide a diagnostic specimen. The ultrasound transducer is carefully cleansed and then soaked in rubbing (70% isopropyl) alcohol for several minutes before the procedure. After the procedure, the transducer is also carefully cleansed. Informed consent is obtained, and the patient is asked about medications and factors that might impair coagulation. In our experience, patients taking aspirin are not at a significantly increased risk of bleeding from an FNA or even a CNB performed with an 18-gauge cutting needle. They are merely told of the slightly increased risk of a post-procedural hematoma. If a patient is taking coumadin and the drug cannot be discontinued, an FNA (and even a CNB with an 18gauge needle) can still be performed, but firm compression must be applied to the biopsy site for at least 5 min after the procedure. Depending on the location of the tumor, the patient is placed in a dorsal decubitus or oblique lateral position to spread the breast on the chest wall and thus

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minimize the length of the needle’s pathway. Local anesthetization is rarely necessary for FNA. The skin is prepared with alcohol, which also serves as an acoustic coupling medium. The standard technique of needle insertion for FNA is the oblique insertion technique, in which the needle is inserted from one end of the transducer along the scan plane with an obliquity that depends on the depth of the target (Fig. 1) [8,9]. With this technique, not only the tip but most of the distal portion of the needle is visualized from the moment it enters the scan plane. In experienced hands, the oblique insertion technique is 100% accurate and safe. Although needle guides that attach to the transducer and maintain the needle within the scan plane are available, the freehand technique is preferred for FNA because it allows reorientation of the needle at different angles and therefore

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permits a larger volume to be sampled. The sampling of a solid mass is performed with to-and-fro movements of the needle to dissociate the tumor tissue, while a moderate (1–3 ml), but constant, negative pressure is applied via the attached syringe. The appearance of blood-tinged material in the needle’s hub confirms that a sufficient amount of material has been accumulated in the needle. The negative pressure is then released, and the needle and syringe are withdrawn. Automatic aspiration devices are available that allow the negative pressure necessary for FNA to be applied with a single hand while the other hand is used to hold the transducer in place for continuous real-time monitoring of the entire procedure. Alternatively, if a short piece of tubing is used to connect the syringe to the needle, an assistant may actuate the syringe while the operator manipulates the needle. Whatever the aspiration technique employed, the sampling process should not take more than 1 min. It is imperative that the correct placement of the biopsy needle in/through the target lesion be adequately documented on film (or, better, that the entire biopsy procedure be videotaped) to prove that samples have been unequivocally obtained from within the lesion, should this become an issue during the patient’s follow-up (Fig. 2).

3.1.2. FNA of cysts and fluid collections Cysts and other fluid collections can be readily aspirated with a fine needle (Fig. 3). On occasion, an 18-gauge needle may be needed to drain an inspissated cyst, which typically contains toothpaste-like material (Fig. 4). In such a case, it may not be possible to drain the cyst completely. When an intracystic tumor is suspected based on sonograms, a pneumocystogram can be obtained after injecting into the cyst a volume of air equal to the volume of fluid aspirated. However, the pneumocystogram is not really necessary for diagnostic purposes since this type of lesion needs to be excised anyway. Pneumocystography may still be useful to confirm that a small indeterminate mass on mammograms was indeed a cyst when the correlation between US and mammography was not clear. Other collections that can be subjected to US-guided diagnostic FNA or percutaneous drainage in the proper clinical setting include postoperative hematomas, lymphoceles, and abscesses.

Fig. 1. Technique of US-guided FNA. (A) Photograph shows the insertion of the needle, attached to a 20-ml syringe, during US-guided FNA. (B) Sonogram shows the tip of the fine needle (arrows) inside the target lesion (arrowheads).

3.1.3. FNA of solid masses FNA of infiltrating ductal carcinomas usually yields highly cellular cytologic specimens; with US guidance, the diagnosis is established with a single pass in the majority of cases (Fig. 5). On occasion, a scirrhous carcinoma may be difficult to sample by FNA. As a rule, an insufficient specimen must be regarded as a failure of the procedure.

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insufficient specimens, usually from hyalinized fibroadenomas; an insufficient specimen should prompt a CNB. Another limitation of FNA is the inability to differentiate a fibroadenoma from a phyllodes tumor, although even CNB may not be able to make that distinction. FNA can also readily establish the definitive diagnosis

Fig. 2. US-guided FNA of a 0.5-cm invasive ductal carcinoma detected by screening mammography. (A) Mammogram shows the minute density (arrow). (B) Sonogram obtained during sampling shows the tip of the fine needle within the suspicious mass.

Other forms of breast malignancy, such as medullary or mucinous carcinomas, lymphomas, or metastases to the breast from extramammary primary cancers, can also be correctly diagnosed cytologically. The hormonal receptor status of carcinomas can be assayed on fine-needle aspirates, although this is usually done on CNB specimens (Fig. 6). Additional tests (e.g. DNA ploidy, Ki-67, Her-2/Neu) can also be performed on cytologic specimens to assess the tumor’s aggressiveness. While the pretherapeutic assessment of a new cancer requires a CNB, the diagnosis of a local recurrence does not, as the only information needed prior to treatment is the confirmation of the similarity of the recurrence to the known primary cancer. This is usually achievable with FNA [10]. When strict cytologic criteria are used, the diagnosis of fibroadenoma can be reliably established with FNA (Fig. 7). The major limitation of FNA of fibroadenomas is the relatively high incidence (up to 20%) of

Fig. 3. (A) Sonogram shows an indeterminate hypoechoic mass (arrow) measuring 0.3 cm. (B) Sonogram obtained during US-guided FNA shows the bevel of the needle in the mass, which was a cyst. (C) Sonogram shows the complete collapse of the tiny cyst.

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Fig. 4. Photograph shows the thick material aspirated from an inspissated cyst.

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cal excision after US-guided localization of the lesion must be considered. False-negative cytologic diagnoses are rare. The possibility that the needle may have missed a small target should always be entertained if the operator has not reached a sufficient level of expertise. It must be kept in mind that the manual skills required for interventional breast US are greater than those needed to perform breast US. Those who cannot achieve a 100% success rate in hitting the target lesion, especially with the freehand technique, may require additional training and supervision or need to use needle guides. True cytologic false negatives may occur with paucicellular and markedly desmoplastic tumors such as infiltrating lobular carcinomas. Tubular carcinomas have also been reported as having the potential to mimic a fibroadenoma cytologically. False-positive cytologic results are even rarer; they have been reported mainly in cases of hypercellular benign lesions such as papillomas, some

of other benign conditions such as fat necrosis, acute inflammation, or even rarer conditions like granular cell tumor or epidermal inclusion cysts [11]. The diagnosis of an intramammary lymph node is readily achieved via FNA. A significant advantage of FNA is to be able to provide a diagnosis within a few minutes, if the cytopathologist is available at the time of the procedure.

3.1.4. FNA of lymph nodes Whenever a definitive diagnosis is needed, US-guided FNA readily confirms (or rules out) metastatic involvement of enlarged lymph nodes in any of the regional nodal basins, including the internal mammary chains (Figs. 8 and 9) [12]. FNA of lymph nodes is easy to perform because of the lymph nodes’ rich cellularity. A single pass should always be sufficient to obtain an adequate specimen from a lymph node. The cytologic diagnosis of benign versus metastatic lymph node is easy to establish, and there is no need to perform a CNB. Care must be taken to sample the node extensively to be able to rely on a diagnosis of benign reactive hyperplasia and exclude a minute associated metastasis hidden in the hypoechoic cortex of a reactive node. In a patient with an FNA-proven breast cancer that requires determination of invasiveness before therapy, the confirmation by FNA of a metastatic lymph node in the axilla provides indirect proof of the cancer’s invasiveness. This information may spare the patient a CNB of the primary breast tumor if determination of invasiveness was the only reason for the CNB to be done. 3.1.5. Failures and limitations of FNA With solid lesions, an insufficient smear must be viewed as a complete failure of the procedure and should prompt another pass. Should a second pass also fail, CNB should be performed right away. Otherwise, surgi-

Fig. 5. Infiltrating ductal carcinoma. (A) Aspiration smear shows a complex epithelial cell group with cribriform arrangement. The epithelial cells are pleomorphic and overlapping with nuclear hyperchromasia and prominent nucleoli. (B) Corresponding tissue section shows infiltrating ductal carcinoma with similar cell arrangement.

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Fig. 6. Immunostain for estrogen receptors shows positive nuclear staining in the majority of the tumor cells.

tubular adenomas, and atypical ductal hyperplasia. Radiation-induced changes can also mimic recurrent carcinoma cytologically [13].

Fig. 8. US-guided FNA of an axillary lymph node metastasis. Sonogram shows the fine needle’s tip in the hypoechoic portion (arrowheads) of the suspicious node (arrows).

It must be emphasized that a significant level of expertise is also required from the cytopathologist and that the best results of US-guided FNA will be achieved if breast imagers and pathologists work as a team with an open line of communication.

3.2. CNB Interest in CNB has been revived with the availability of automated spring-loaded devices that activate a 14- to 18-gauge Tru-Cut-type cutting needle in a fraction of a second [14].

3.2.1. Equipment and technique Numerous commercially available devices provide automatic propulsion of a cutting needle with a throw of about 2 cm. A clear understanding of the mechanism of

Fig. 7. Fibroadenoma. (A) Sonogram obtained during sampling shows the needle (arrowheads) in the center of an oval, smoothly demarcated hypoechoic mass (arrows). (B) Typical aspiration smear shows a branching group of cohesive epithelial cells and bipolar stripped nuclei in the background.

Fig. 9. US-guided FNA of an internal mammary node metastasis. Transverse sonogram of the left parasternal region shows the oblique fine needle penetrating the enlarged lymph node (arrowheads). Note the internal mammary vessels (arrows). S, sternum; L, lung.

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Fig. 10. Technique of US-guided CNB. (A) Diagram shows the pre-firing position of the needle, which is parallel to the underlying chest wall. (B) Diagram shows the post-firing position of the needle, which has traversed the target lesion.

the device and knowledge of the location from which the core will be taken are prerequisites to the use of the device. Although the 14-gauge Tru-Cut-type needle has been considered a standard for CNB, high-quality specimens can be obtained with smaller (18-gauge) cutting needles, which cause less trauma. The procedure is explained in detail to the patient, and informed consent is obtained. Before the actual biopsy is started, the firing mechanism of the biopsy device should be tested and the device cocked and locked in the safety position (if a safety lock is available). The site of entry and pathway of the needle must be carefully planned. Then, the skin and transducer are disinfected using povidone-iodine (Betadine). Local anesthesia with lidocaine is administered along the planned pathway of the core biopsy needle, preferably under real-time US guidance. A small skin incision is then made if a 14-gauge needle is used, but this is not needed with an 18-gauge needle. Because of the automatic throw of the needle, the cutting needle must be inserted as horizontally as possible (Fig. 10). This requires that the needle be inserted at a sufficient distance from the end of the transducer. Because the needle is nearly horizontal (i.e. perpendicular to the ultrasound beam), its visualization on the monitor is optimal. However, because there is currently no commercially available guide that can guarantee the safe, nearly horizontal insertion of the needle along the US scan plane, CNB has to be done with the freehand technique. The risk of injury to the underlying chest wall and lung should be constantly kept in mind when

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selecting the entry site and pathway of the needle, monitoring the direction of the needle, and anticipating the post-firing position of the needle tip, especially in small-breasted women (Fig. 11). As a result, CNB requires more experience in US guidance of needles than does FNA, especially when very small and deep lesions are targeted. Under US guidance, the tip of the needle is brought into contact with the mass, the perfect alignment of the needle with the scan plane is verified, and a hard copy of the pre-firing position of the needle is taken. The mechanism is then fired, and a post-firing hard copy showing the needle traversing the target is also recorded. To ensure that the needle is actually traversing a minute lesion and to exclude a volume-averaging artifact, the transducer must be swiveled 90° and a transverse sonogram obtained to show the cross section of the needle inside the target (Fig. 12) [15]. An apparent bending of the portion of the needle that traverses the mass is sometimes demonstrated when the mass is surrounded by fat. This is a useful propagation-speed ultrasound artifact that indicates that the needle has penetrated a medium of different acoustic impedance from that of the sur-

Fig. 11. Technique of US-guided CNB. (A) For a lesion located in the medial breast, the biopsy needle should be inserted with a medial to lateral approach so the needle stays away from the chest wall. (B) For a lesion located in the lateral breast, the patient is turned to the contralateral side to spread the lateral breast over the chest wall. The needle is inserted with a lateral to medial approach.

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with large (14-gauge) needles, an introducer can be inserted first and brought in contact with the lesion; this permits easy and atraumatic reinsertion of the needle for repeat passes and may reduce the risk of seeding malignant cells along the needle track [17]. However, in small breasts and superficial lesions, such an introducer may be easily dislodged. With 18-gauge cutting needles, which are sharper than regular 14-gauge Tru-Cut needles, there is no difficulty reinserting the needle through the skin and subcutaneous tissues for each additional sampling, and thus there is no need for an introducer.

3.2.2. Core biopsy using 6acuum-assisted de6ice A handheld version of the 11-gauge Mammotome device (Ethicon Endosurgery, Cincinnatti, OH) has been designed for use with US guidance. Advantages of the device include a single insertion of the device, convenient automatic core retrieval, and multiple large contiguous samples with the potential to entirely remove small masses [18,19]. In the United States, the device has been approved for biopsy, not for therapeutic purposes. Disadvantages of the Mammotome include its large size and thus greater associated trauma and the cost. While such vacuum-assisted core biopsy devices and the large volume of the cores they yield are well adapted to stereotactically guided biopsy of microcalcifications, they are not needed for the tissue diagnosis of breast masses. Fig. 12. US-guided CNB of a small carcinoma. (A) Post-firing sonogram shows the brightly echogenic 18-gauge cutting needle (arrows), which has traversed the hypoechoic tumor (arrowheads). (B) Orthogonal view confirms the correct placement of the biopsy needle by showing its cross section (arrow) in the center of the mass (arrowheads).

rounding fat (Fig. 13) [16]. During CNB of scirrhous tumors, it is not exceptional to observe some deviation of the cutting needle into the periphery of the mass, especially with an 18-gauge Tru-cut-type needle, whose stylet may actually bend. In such cases, the use of a stiffer 16-gauge or 14-gauge needle is recommended, although these larger but also relatively blunt needles may not pierce the very firm tumor any better than the sharper 18-gauge needle. After the post-firing sonograms are obtained, the needle is withdrawn and the tissue core recovered. The procedure is repeated in different areas of the tumor until a sufficient number of satisfactory cores have been obtained. In our experience, when the transfixion of the target has been clearly documented with US and cores appear to be of satisfactory size, no more than four cores obtained with an 18-gauge cutting needle are needed for diagnosis. To avoid repeat passage through (and trauma to) the subcutaneous tissues when multiple cores are obtained

3.2.3. Processing of cores The cores are usually placed in a solution of formalin for overnight fixation. If the diagnosis of cancer needs to be confirmed more rapidly, an FNA pass with rapid stain can be done. In rare cases, US-guided CNB is done to sample an extensive area of microcalcifications without a discrete mass. In such cases, it is imperative to process the cores in the same manner as they would be if the biopsy was done under stereotactic guidance; i.e. the cores obtained must be radiographed using a mammographic unit and magnification technique or dedicated equipment for specimen radiography (e.g. Faxitron, Faxitron X-ray Corporation, Wheeling, IL) to document the presence of the calcifications in the cores (Fig. 14). 3.3. FNA 6ersus CNB Advantages of US-guided FNA include its pinpoint accuracy, the excellent tolerance by patients, and the ability to aspirate or inject fluid or air. The accuracy of the monitoring of the needle’s placement in experienced hands is synonymous with total safety, and lesions that lie close to the chest wall or to breast implants can be safely aspirated (Fig. 15) [20]. Also, results can be obtained within minutes. The disadvantages of FNA include the absolute requirement for an expert cyto-

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pathologist, the failure to yield adequate material in cases of fibrous tumors, and the inability to differentiate between invasive and noninvasive breast carcinoma, which requires histopathologic examination of a core. Advantages of CNB include a near 100% tissue recovery rate even in fibrous masses, the ability to assess the invasiveness of the cancer, and the fact that tissue cores are readily interpreted by any pathologist. However, compared with FNA, CNB is more invasive, with a higher rate of bleeding complications, and the risk of malignant seeding along the needle track (reported with the use of 14-gauge needles) may be more significant than with FNA [21,22]. There is significant variation in the results reported in the literature for both US-guided FNA and CNB, which underscores the operator dependence of both

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sampling techniques as well as of US itself [23–34]. Variations are also attributable in some cases to the fact that some authors exclude the nondiagnostic results from their calculation, which results in overestimated accuracy values [35]. FNA and CNB should not be considered as opposing techniques but instead should be viewed as two facets of the same procedure, the percutaneous breast biopsy. In institutions where an expert cytopathologist is available, the radiologist should be expert in both techniques and determine on a case by case basis whether the lesion in question should be sampled with CNB or FNA (Table 1). The goal to be kept in mind is that at the end of the procedure, a definitive tissue diagnosis must be available so that decisions can be made regarding the management of the patient.

Fig. 13. Artifactual ‘bending’ of the needle during needle biopsy. (A) Diagram shows the artifactual deformity of the needle caused by a faster ultrasound propagation speed in the interposed portion of the tumor than in the adjacent fat. (B) US-guided CNB of a small carcinoma. Note the apparent bending of the needle (arrows) in its course through the tumor. (C) Sonogram obtained during US-guided FNA of a solid mass shows the apparent deformity of the needle at its entry into the mass (arrow) (‘bayonet’ sign).

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As a rule, microcalcifications cannot be optimally imaged with US, and their biopsy remains the domain of stereotactic guidance.

3.5. Keys to success of US-guided needle biopsy US-guided needle biopsy of nonpalpable breast lesions requires teamwork. Progress can be made and experience accumulated only through ongoing communication between the radiologist, the pathologist, and the surgeon. US-guided interventional procedures require excellent eye–hand coordination and a significant amount of practice before the mandatory 100% accuracy level in hitting the target can be reached. Practicing with easyto-make phantoms shortens the learning curve of beginners [36]. The golden rule in breast biopsy is the concordance between the results of the biopsy, imaging, and physical examination. Any discrepancy, e.g. a negative result of needle biopsy in the face of a single suspicious finding—physical, mammographic, or sonographic— should prompt careful reevaluation and should not delay surgical excision. 4. Other US-guided interventional procedures

4.1. Percutaneous galactography When cannulation of a duct that is causing discharge cannot be performed for technical reasons and the Fig. 14. US-guided CNB of a cluster of malignant calcifications. (A) Pre-firing sonogram shows the needle (arrows) aligned with a cluster of microcalcifications (arrowheads). (B) Radiograph of the cores obtained confirms the presence of microcalcifications in the specimen.

3.4. US 6ersus stereotactic guidance For masses that can be demonstrated with US (the vast majority), advantages of US guidance over stereotactic guidance of needle biopsy include the ability to use the shortest route to the lesion, the unique real-time monitoring of both the placement of the needle and sampling of the lesion, the multidirectional sampling with FNA, the rapidity of the procedure, the comfort of the patient, the applicability to virtually any mass in the breast or in node-bearing regions, and the wide availability of US equipment. For nonpalpable lesions visualized only by US, US is the only guidance technique to be used. In breast imaging centers, both US and stereotaxy should be available for guiding needle biopsy of nonpalpable lesions. In dedicated centers so equipped, the wave of popularity of stereotaxy has been reversed, and biopsy of the vast majority of nonpalpable masses is now guided by US rather than stereotaxy.

Fig. 15. US-guided FNA of a carcinoma adjacent to the anterior wall of a breast prosthesis. Sonogram shows the fine needle in a poorly defined tumor (arrows). P, prosthesis.

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Table 1 Indications for US-guided FNA or US-guided CNB US-guided FNA Cystic mass (including possible inspissated cyst and abscess) New suspicious/malignant-appearing mass by imaging Local recurrence of breast cancer Benign-appearing, fibroadenoma-like solid mass Probable fat necrosis (e.g. in a reconstructed breast) Indeterminate/suspicious node in axilla, internal mammary chain, supraclavicular fossa, or neck (including intramammary node) Failure of FNA of a solid mass

dilated duct can be demonstrated on US, antegrade galactography by direct percutaneous injection of contrast medium into the duct can be performed [37,38].

4.2. Preoperati6e localization of nonpalpable masses Localization of nonpalpable masses detected by mammography and/or US can be achieved with US pre- or intraoperatively. The same localizing techniques that are used under mammographic guidance can be used with US guidance. With US guidance, the localizing device (usually a hookwire) is inserted through the mass, which helps to anchor the needle in place. US has the advantage of providing the shortest distance from the entry site of the localizer to the mass, which is greatly appreciated by the breast surgeon. US can be used when mammography cannot, e.g. when the breast is very small, when the mass is very close to the chest wall or to an implant, and when the lesion is not clearly seen on mammograms. Obviously, masses detected by US alone must be localized with US. In general, when a nonpalpable tumor has been visualized by both mammography and US, US-guided localization should be preferred because it is faster and therefore better tolerated by the patient than mammographically guided techniques.

US-guided CNB

× × × × × ×

×

×

sterile preparation of the patient, which allows the radiologist to use nonsterile equipment. We use an ultrasound scanner that is permanently based in the surgery department, although a small portable scanner with a 7.5-MHz probe would be acceptable in almost all cases. Transportation-related delays and frustrations to both the patient and surgeon are avoided, and the only timing issue is for the radiologist to precede the surgeon into the operating theater by a few minutes. A significant advantage of intraoperative localization is that it allows the radiologist and the surgeon to communicate directly and discuss the real-time images of the tumor. As the surgeons at our institution have become more familiar with this approach, the number of requests for placing a localizing needle has decreased; most localizations in small to medium-sized breasts can be done by simply marking the projection of the mass on the skin with an X and indicating the depth of the lesion to the surgeon (Fig. 16). If it is believed that the lesion is too deep and/or the breast is too large for simple skin marking, a localizer (hookwire or loop needle) is inserted at that time. It is expected that some breast

4.3. Intraoperati6e localization of nonpalpable masses For the past 10 years, we have been localizing nonpalpable breast masses with US in the operating room [39]. Our successful experience with intraoperative US has been confirmed recently by several studies at other institutions, and interest in this procedure is growing in the surgical community [40– 42]. Because intraoperative US localization is done with the patient placed in the operating position, the risk of the localizing needle or hookwire being dislodged by changes in the patient’s position is eliminated. The localization is done while the patient is under anesthesia (general or local), which avoids stress and discomfort to the patient, and before

Fig. 16. Intraoperative ultrasound localization of a nonpalpable mass in the right breast. The projection of the mass has been marked on the skin with an X in the 9 o’clock position. A focal dilatation of a duct has also been marked on the skin. All markings were made in the presence of and discussed with the surgeon.

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5-mm-long, 18-gauge stainless steel rods are inserted in the (residual) tumor and deposited in slightly different directions, to increase the reflectivity of the cluster of markers (Fig. 18). We have also tried using a commer-

Fig. 17. Ex vivo sonogram of a freshly excised lumpectomy specimen shows the 0.3-cm carcinoma (arrows) that had been localized with US in the operating room.

surgeons will want to use continuous intraoperative US to monitor their progress toward the lesion and to ensure the adequacy of the excision margins [40–42].

4.4. US of the surgical specimen US confirmation of the successful excision of a lesion that was detected by US but not by mammography (and for which radiography of the specimen is therefore not relevant) can be obtained by scanning the freshly excised specimen placed in a container filled with saline (Fig. 17). Failure to visualize the mass in the specimen should prompt the radiologist to scan the area of the wound to identify the residual mass and further guide the surgeon [43].

4.5. Placement of markers in tumors responding to preoperati6e chemotherapy Since 1995, we have been implanting metallic markers under US guidance in and/or adjacent to breast carcinomas that are responding significantly to preoperative chemotherapy [44]. The goal is to allow the surgeon to locate and excise the tumor bed should the tumor disappear completely during chemotherapy. This has become a significant issue since most breast cancer patients at our institution undergo preoperative chemotherapy; only patients who have a carcinoma that is less than 2 cm in diameter and that is node-negative are not offered preoperative chemotherapy. Markers are implanted in tumors that respond significantly after two courses of chemotherapy or at the time of diagnosis if the tumor is small. Using a 15gauge needle and a blunt stylet, four custom-made

Fig. 18. Insertion of metallic markers in carcinomas that respond well to preoperative chemotherapy. (A) Four metallic markers (arrows) with their distinctive comet-tail artifact are being inserted through a 15-gauge needle into the small residual tumor (arrowheads). (B) Sonogram obtained after completion of preoperative chemotherapy in a different patient shows a metallic marker (arrow) with a characteristic comet-tail artifact (arrowheads). Note that there is virtually no residual tumor.

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4.6. Sentinel node mapping in patients with nonpalpable breast cancer Pathologic examination of sentinel lymph node(s) in the axilla has been proposed as an effective way to reduce the number of unnecessary axillary node dissections in breast cancer patients. The rationale is that the histopathologic status of the sentinel node(s) reflects that of the rest of the axilla. Two basic methods are used to identify sentinel nodes. One method involves lymphoscintigraphy after direct injection of technetiumlabeled sulfur colloid around the primary tumor. Another method involves the injection of a vital dye (isosulfan blue) around the tumor in the operating room just prior to surgery. In both cases, the injection around nonpalpable lesions can be performed more accurately under real-time US guidance.

4.7. US-guided percutaneous ablation of breast masses

Fig. 19. (A) Photograph shows an embolization coil (arrow) and insertion kit for marking the tumor bed before or during preoperative chemotherapy. (B) Sonogram shows the C-shaped coil (arrow) inside the residual tumor. Note the absence of a typical comet-tail artifact.

cially available platinum embolization coil (MCE-35P-12-VA coil, Cook Group Inc., Bloomington, IN) as a marker (Fig. 19). The advantage is the absence of any risk of migration, whereas the disadvantage appears to be lesser sonographic visibility of the coil compared to the cluster of rods, which has led to the current technique of inserting two adjacent coils. There is still a need for development of a marker to tag the tumors treated with preoperative chemotherapy—one that would be easy to place, be visible with US in all cases, and have no risk of migration or disappearance during the treatment period. After completion of the preoperative chemotherapy, the breast is reassessed. If the metallic markers can be identified on US through their distinctive comet-tail artifact, localization of the tumor bed is done in the operating room with US. If the markers cannot be seen on US, which occurs in about 20% of cases with the use of the rods [44] and possibly more often with the use of coils, then the localization of the markers is done preoperatively with mammography.

A new application of interventional breast US is the guidance of percutaneous ablation of breast masses. Pilot studies are underway that use cryotherapy, radiofrequency, or laser to ablate such masses and real-time US to guide the accurate placement of the ablating device and to monitor the procedure. We have been performing US-guided radiofrequency ablation of small (T1) breast cancers. The radiofrequency probe (RITA Medical Systems, Mountain View, CA) is inserted into the tumor, and a total of nine electrodes (antennas) are deployed through the tumor under US guidance (Fig. 20). After the correct placement of the needle-electrode has been confirmed by US (Fig. 21), the probe is connected to the radiofrequency generator. Temperature-sensing thermocouples located at the tips of five of the antennas provide real-time monitoring of the temperature achieved at the periphery of the ablation zone. The temperature is gradually increased to the target temperature (95 °C) over a period of 5–7 min. The temperature at the tips of the antennas is maintained for 15 min, followed by a 1-min cool-down period before the prongs are retracted and the probe is removed from the breast. Our preliminary experience has shown that 100% ablation is achievable with this technique (Fig. 22) [45,46].

5. Conclusions Because of its unique real-time capability, US is preferred to stereotaxy for guiding needle biopsy of nonpalpable breast masses, and US is used more and more frequently for preoperative localization of such lesions. It should be kept in mind, however, that US is a more operator-dependent modality than stereotaxy is and that the amount of experience required in US-

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B.D. Fornage et al. / European Journal of Radiology 42 (2002) 17–31

Fig. 21. Longitudinal sonogram shows the deployed prongs (arrows) through the hypoechoic tumor.

Fig. 20. Equipment used for radiofrequency ablation of breast cancer. (A) Radiofrequency generator (RITA Medical Systems, Mountain View, CA) with a laptop computer for the real-time graphic display of the temperatures in the target lesion. (B) Needle-electrode with its 9 prongs deployed.

guided interventional procedures is inversely related to the size of the target lesion. There is growing interest in US-guided ablation of breast masses among the surgical community. The best results are to be expected when the team includes a radiologist experienced in interventional breast US. References [1] Gui GP, Allum WH, Perry NM, Wells CA, Curling OM, McLean A, et al. One-stop diagnosis for symptomatic breast disease. Ann R Coll Surg Engl 1995;77:24 – 7. [2] Fornage BD. Ultrasound of the breast. Ultrasound Quarterly 1993;11:1 – 39.

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