Localized fibrous pleural mesothelioma: CT findings

The CT findings in 16 patients [2O examinations] with proven Iocnlized j?brous mesothe!ioma are described. These iesions proved to be large, uninvasive, somekres heterogeneous, and enhancing solitary masses. These morpho!ogic findings in an asymptomotic potienl should be suggestive of this lesion. KEY woRi)s:

Localized

f%rous

meso~helioma;

Pleura;

CT

Localized fibrous mesothelioma is a well described unusual pleural tumor (I-6). Though this lesion may recur (I, z), its behavior is biologically benign and clearly different from malignant mesothelioma, the latter being an asbestos-related illness. eral reports concerning the computed tomographic /CT) features of this disease have appeared (7-10). The largest of these described the findings in six patients (7). The above reports have stressed the homogeneous, lobular, univasive nature of these lesions. They are often mobile, may occur in fissures, and usua!ly non-cakified. Identification of a pedicle was described in one patient [6), We describe the features patients with this entity. 8ur findings as enumerated below, differ with several of the above reports.

From the Department of Radiology, The Mount Sinai Medical Center, CUNY, Gew York (D.S.M.]; HGtel Dieu, Paris, France (EM., I.N.B., I.P.]; Division of Cardiothoracic Surgery, Tne Mount Sinai Medical Center, CUNY, New York (P.A.K.). Address reprint requests to: Dr. David S. Mendeison, Box 1234, Deoartmeni of Radioioev. Mount Sinai Medical Center. One Gust&e L. Levy Race, M&G York, NY 10029-6574. Received September 1990; revised January 1991. 0 1991 by Elserier Science Publishing Co., Inc. 655 Avenue of the Americas, New I’m-k, NY iO010 0899170711911$3.50

Sixteen patients underwent 20 ST examinations, which we retrospectively analyze. Twelve patients lad an exam at the time of their initial presentation. 3ne of these patients bad a SolSow-up exam prior to surgery, two years after the first exam. One patient was evaluated for a first recurrence. were each evaluated for first and seco 16 exams). iNineteen surgical resections were conducted on these 16 patients, seven of the resections jeing on recurrent tumors. These seven latter resec:ions occurred in four patients, The 20 studies were pe on a variety of CT scanners with different te , Four studies had no iodinated contrast administered, six with contrast oth with and without intravenous conld not establish with certainty the rate of contrast infusion. AI1 patients in this report u cotomy performed, thus provi

The 16 patients evaluated consisted of 12 women and 4 men. Their ages ranged from 3 to 73 [two patients ages were unavailable). The lesions greatest CT diameter averaged 7.8 cm and. ranged from 4 to 17 cm. CT measurements could only be obtained on 13 of these patients retrospectively, as complete exams with me~s~r~rne~t grids always available. Specimen diameters w on 15 resected specimens and averaged a range of 5.5 to 25 mm, Enhancement characteristics were judged by visual ~~~~~ct~~~ in the 16 examinations in which csntrast was CT numbers were generally not availa enhanced at least to the same extent as other soft tissues, particularly muscle, with seven studies dem-

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E I. A 73-year-old woman presented in 1984 with dyspnea and hypertrophic pulmonary osteoarthropathy. A demonstrated CXR (A) performed in 1972 retrospectively an abnormal diaphragmatic silhouette (arrows). A CT (i%J performed at presentation demonstrated a large mixed attenuation mass. Note the necrotic center, ring of enhancement, and lack of invasiveness despite the large size. No chest-wall invasion was noted on any CT section. A large localized fibrous mesothelioma was resected, A small pedicle from the visceral pleural was found at thoracotomy.

onstrating enhancement greater than the soft tissues. Enhancement was homogeneous in 10 patients and heterogenous in 6. Areas of necrosis (Figures 1 and 21, always central, were noted on four examinations. Calcifications were noted in only two different patients (Figure 2). Four patients were noted to have a pedicle (Figure SC). The angle formed between the mass and the chest wall was acute in 15 examinations, obtuse in four examinations and had both features in one examination. Retrospectively we were able to determine that four patients had masses growing slowliy for periods of 4 to 13 years. Three other patients had masses present for three years prior to surgery. We could not establish the duration of the lesion in the other patients. Of the seven recurrent lesions, the interval between recurrences averaged six years, with a minimum of two years and a maximum of 15 years.

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Nine of Ihe 16 patients were asymptomalic. The remaining patients complained of either chest pain, often vague in nature, or shortness of breath. In five patients another diagnosis was strongly suspected preoperativeiy; thymoma (a), neural tumor (21, and pericardial cyst (I).

E 2. A SS-vear-old woman with dyspnea .Liatla CT, with contrast, of a-large mass. Note the central necrosis and calcification. Again despite the large size this fibroma is uninvasive.

E 3. [_A)This woman has ~3 &normal CXR in 1963. i in 1972 at the time of the CXR shcwn here, a thoracotomg was performed and iocalized fibrous pleural mesothelioma was removed. ,Gj. In 1983 the patient re-

turned with the recurrence shown here. The CT, without contrast, demonstrates the pedicle of origin at the apex, laterally. This patient had a second recurrence in 1987. 3nce again the tumor was localized to the left hemithorax. Iiovvever, it could not be totally resected. and wzs caIle$ nalignant at this time.

Localrzed fibrous pleural mesothelioma is an unusual but well-described entity. The presentations of our patients were similar to those of prior series (2-4). Of note, these lesions were often large (average CT diameter = 7.8 cm) and better than half (9 of 16) of the patients were asymptomatic. Many of the lesions had been present and growing slowly for several years. This combination should lead one to entertain this diagnosis. CT is usually performed at some point in the evaluation of a chest imass. The largest reported series of CT exams was in six patients (7). Our study corroborates

many of the conclusions oi those aurhorsF but differs 1n a few respects. Of particular note was the heterogen~us pattern of enhancement in six of the 16 examiwas administered. Such nations in which contrast heterogeneity was rare (1 of 6) in the prior reports [T-IQ). In our patients the heterogeneity was characterized by central areas of decreased attenuation surrounded by a region of homogeneous enhancement. Pathologically, these areas prove to be areas of cystic aecrosis and hemorrhage. This Ending tended to occur in the larger lesions with the smaller lesions appearing homogeneous. This feature has been described in the pathology literature (3, 4). We believe that in seven studies, the lesion en-

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ET AL.

hanced more than the soft tissues. We feel this is a significant finding despite our recognition of the limitation that this observation is on the basis of visual inspection and not CT numbers (Figure 1B). This is because many of these exams were performed at different institutions and only the hard copy of the exam was available to us. In addition, the means of contrast administration, bolus or drip infusion, was usually not known to us, Despite these limitations, we believe that in a significant percentage of examinations the lesion enhanced more than soft tissues. This observation differs from that of earlier authors (7-101. It may well be that the timing of the contrast administration greatly effects the degree of enhancement. Dynamic CT, carried out over a protracted period of time (as in a hepatic hemangioma scan] might provide useful information regarding enhancement character. Despite the pleural origin of these lesions, the mass formed an acute angle with the adjacent structures in 15 of 20 exams. This consistent feature, atypical of pleural lesions may be accounted for by the large size of the lesions and the fact that pathologically they arise from a pedicle and may “hang” into the adjacent parenchyma. The origin from a pedicle presumably accounts for the mobility of this lesion, a feature that can be demonstrated by decubitus positioning of the patient (2, 8). A pedicle could only be identified in four patients on the CT exam. When identified, the presence of the pedicle can be a useful diagnostic point (8). As in other series, pleural effusions were present but rare. We identified calcium in two patients. While not a common finding (3,4,7), calcification can occur and certainly its presence should not exclude this diagnosis. Though considered a benign lesion, four patients in our series were operated on for first and/or second recurrences, in the thorax (Figure 3). The behavior of this lesion can be more aggressive than that expected of benign neoplasms; however, the biologic behavior is clearly not that of malignant mesothelioma, usually a fatal illness. The wrong diagnosis was strongly suspected in five patients. In each of these patients the primary factor was the misidentification of the site of origin of the tumor. A paramediastinal location led to CODsideration of a differential diagnosis of masses in

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mediastinai or paraspinal compartments. Xecognizing that these relatively large masses are pleurall irr origin appears to be a prospective problem. The formation of an acnte angle with the chest wall is misleading in this regard. The criteria suggested by drick (73 of a smoothly tapering margin with the chest wall might be helpftll. These findings are unusual in other pleural neoplasms (91. Pleural fluid collections do not resemble these localized fibromas and should not be a source of confusion. In conclusion our series of patients corroborates many previous observations. Two findings at with prior reports are lesion enhancement an more common appearance of heterogeneity, including necrosis and calcification. We would agree with prior authors that there are no pathognomonic CT findings. Mowever, the ability of CT to confirm the solitary nature of the lesion and the lack of invasion, in combination with a lack of symptoms can lead one to strongly suspect this diagnosis.

1. Mascie-Taylor BH, Knox AJ, Wordman AG, Page RL. Recurrent pieural fibroma Br J Dis Chest 1986;80:90-91. 2. Okike N, Bern& PE, Woolner LB. Localized the pleura. Benign and malignant variants. vast Surg 1978;73:363-370.

mesothehoma of J. Thorac Cardio-

3. Briselii M, Mark EJ, Dickerson GR. Solitary fibrous tumors of the pleura: eight new cases and review of 360 cases in the literature. Cancer 1981;47:2678-2689. 4. Scharifker D, Kaneko M. Localized fibrous “Mesothelioma” pleura (Submesotheliai fibroma). A clinicopathologic study 18 cases. Cancer 1979;43:627-635.

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5. Lewis MI, Horak DA, Yellin A, Rotter A, Be!man MJg Benfield JR. The case of the moving intrathoracic mass, Chest 1985;86:897-898. 6. Clagett OT, IMcDonald sotheiioma of the 1952:24:212-230.

JR, Schmidt HW. Locaiized fibrous me1 Thorac Cardiovasc Surg pleura.

7. Dedrick CG: McLoud TC. Shepard JO, Shipley R. Computed tomography of localized pleural mesothelioma. AJR i985;144:275-280, GL, Yee AC. Computed tomographic 8. Weisbrod pedunculated fibrous mesothelioma. J Can 1983;34:147-148. 9. Williford ME, Hidalgo H, Putman Tomography of Computed 1983;140:909-914.

diagnosis of a Assoc Radio1

GE, Korobkin M, Ram PC. pleural AJR disease.

10. Spizarry DL, Gross BH, Shepard JO, CT findings in localized the pleural fissure. JCAT fibrous mesothelioma of 13:1986;942-944.