DOI: 10.1148/rg.263055211
RadioGraphics 2006;26:923-940
From the Archives of the AFIP
Pleuropulmonary Synovial Sarcoma1
Aletta Ann Frazier, MD,
Teri J. Franks, MD,
Robert D. Pugatch, MD and
Jeffrey R. Galvin, MD
1 From the Departments of Radiologic Pathology (A.A.F., J.R.G.) and Pulmonary and Mediastinal Pathology (T.J.F.), Armed Forces Institute of Pathology, 14th St and Alaska Ave NW, Washington, DC 20306-6000; and the Department of Diagnostic Radiology, University of Maryland School of Medicine, Baltimore, Md (A.A.F., R.D.P., J.R.G.). Received December 15, 2005; revision requested January 18, 2006 and received February 15; accepted February 20. All authors have no financial relationships to disclose.
Address correspondence to A.A.F. (e-mail: frazier{at}afip.osd.mil).
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Abstract
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Pleuropulmonary synovial sarcoma (PPSS) is increasingly recognized as a subtype of sarcoma because of the recent identification of a distinctive chromosomal translocation specific to synovial sarcoma. Soft-tissue synovial sarcoma is far more common than PPSS and typically develops in para-articular locations of the extremities; affects young and middle-aged adults, with no difference in distribution between the sexes; and has well-documented radiologic manifestations. PPSS may arise in the chest wall, heart, mediastinum, pleura, or lung, and it shares patient demographics and several imaging features with its soft-tissue counterpart. Patients present with a cough, chest pain, or dyspnea. On chest radiographs, PPSS typically appears as a sharply marginated mass with uniform opacity, based either in the pleura or in the lung, and often accompanied by an ipsilateral pleural effusion. Computed tomographic images show a well-circumscribed heterogeneously enhanced lesion without associated involvement of bone and without calcifications (except in the case of a chest wall primary tumor). Magnetic resonance imaging provides superior demonstration of nodular soft tissue and multilocular fluid-filled internal components of PPSS, in addition to peripheral rim enhancement after the intravenous administration of a gadolinium-based contrast material such as gadopentetate dimeglumine. Current treatment consists of surgical resection followed by chemotherapy, radiation therapy, or both.
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LEARNING OBJECTIVES FOR TEST 6
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After reading this article and taking the test, the reader will be able to:
- Describe the patient demographics, clinical manifestations, and pathologic features of pleuropulmonary synovial sarcoma (PPSS).
- Identify the radiologic features that characterize PPSS and that help distinguish it from other primary neoplasms in the chest.
- Plan the optimal imaging approach for evaluating the origin and components of PPSS.
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Introduction
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Pulmonary sarcomas constitute only 0.1%–0.5% of all primary lung malignancies. The most frequently reported subtypes of sarcomas in the lung are leiomyosarcoma, malignant fibrous histiocytoma, fibrosarcoma, and, more recently, synovial sarcoma (1). The term synovial sarcoma first appeared in the German surgical literature in 1865, where it was used to describe a complex multi-nodular lesion apparently arising from synovial tissue in the knee of an adult patient (2). Fifty years later, in 1910, French authors Lejars and Rubens-Duvall published a description of the classic pathologic features (3). In 1947, the Armed Forces Institute of Pathology (AFIP) presented the first notable series of synovial sarcoma cases, a group of 32 lesions that were termed "synoviomata." These cases were registered at the AFIP during World War II (3).
Currently, synovial sarcoma accounts for 7%–10% of all soft-tissue sarcomas. The most common sites of origin are the thigh, knee, ankle, foot, and upper extremity (4,5). In unusual cases, synovial sarcoma may arise within the chest wall, mediastinum, heart, lung, or pleura (4,6–11). Increasingly sophisticated diagnostic techniques in immunohistochemistry, electron microscopy, and cytogenetic analysis have led to more frequent recognition of PPSS as a distinct histologic subtype of sarcoma in the lung (1,5,12). In this article, we describe the characteristics of PPSS on the basis of a retrospective review of 12 cases from the archives of the Department of Radiologic Pathology at the AFIP as well as a broader review of the literature.
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Review of Cases
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Twelve cases of PPSS, an anatomic subset defined as synovial sarcoma arising in the lung or pleura, were identified in the archives of the Department of Radiologic Pathology at the AFIP (13). For the purposes of our case review, we included synovial sarcomas that arose in either the lung or pleura, and we excluded tumors that arose in the chest wall, heart, great vessels, and mediastinum. In one patient, the original histopathologic diagnosis was pulmonary blastoma. Clinical information included records of the clinical presentation, surgical reports, pathology reports, and hospital discharge summaries. Conventional chest radiographs were available for 10 of 12 patients, contrast material–enhanced computed tomographic (CT) images for 11 of 12, magnetic resonance (MR) images for three of 12, and fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT images for one of 12. The images were reviewed retrospectively by three radiologists (A.A.F., J.R.G., R.D.P.). Available photographs of gross specimens and hematoxylineosin (H-E)–stained tissue sections were reviewed by a pulmonary pathologist (T.J.F.) with two radiologists (A.A.F., J.R.G.). The data collected during this review are shown in the Table.
Clinical Features
Patients ranged in age from 17 to 68 years (mean age, 37 years). Men and women were affected almost equally (M/F ratio, 1:1.4). The most common symptoms at presentation were dyspnea (seven of 12 patients) and chest pain (five of 12 patients). Three patients had a cough, four reported back pain or shoulder pain, and one exhibited upper extremity swelling. One patient experienced wheezing, and another reported hemoptysis.
Radiologic Findings
We reviewed conventional chest radiographs in nine cases, CT images in 11 cases, MR images in three cases, and PET/CT images in one case. Seven of the lesions were located on the right side, and five were located on the left. The mass was defined by sharply marginated borders with round, ovoid, or lobulated contours on seven of the nine chest radiographs (Figs 1a, 2a, 3a, 4a, 5a). In three cases, the mass was manifested as opacification of more than 50% of the involved hemithorax on chest radiographs, CT images, or both; one of these cases demonstrated a contralateral shift of mediastinal structures (Fig 6). On all chest radiographs, the mass appeared homogeneous, and there was no evidence of cavitation, calcification, or lymphadenopathy. The contralateral lung was normal. Some of the masses appeared to merge at an obtuse angle with the pleural margin (Fig 3a), but confident localization was often difficult on radiographs (Figs 1a, 2a, 3a, 4a).
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Figure 1a. PPSS in a 54-year-old woman with a cough. (a) Posteroanterior chest radiograph depicts a left hilar mass. The visibility of hilar structures (arrow) indicates that the mass is not contiguous with the hilum. (b) Contrast-enhanced CT scan depicts a heterogeneous, low-attenuation mass partly surrounded by atelectatic lung tissue (*). (c) Photograph of the gross specimen shows a bosselated mass adherent to the visceral surface (arrows) of atelectatic lung tissue (black asterisk). Lighter-colored normal lung tissue (white asterisk) is visible at the right.
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Figure 1b. PPSS in a 54-year-old woman with a cough. (a) Posteroanterior chest radiograph depicts a left hilar mass. The visibility of hilar structures (arrow) indicates that the mass is not contiguous with the hilum. (b) Contrast-enhanced CT scan depicts a heterogeneous, low-attenuation mass partly surrounded by atelectatic lung tissue (*). (c) Photograph of the gross specimen shows a bosselated mass adherent to the visceral surface (arrows) of atelectatic lung tissue (black asterisk). Lighter-colored normal lung tissue (white asterisk) is visible at the right.
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Figure 1c. PPSS in a 54-year-old woman with a cough. (a) Posteroanterior chest radiograph depicts a left hilar mass. The visibility of hilar structures (arrow) indicates that the mass is not contiguous with the hilum. (b) Contrast-enhanced CT scan depicts a heterogeneous, low-attenuation mass partly surrounded by atelectatic lung tissue (*). (c) Photograph of the gross specimen shows a bosselated mass adherent to the visceral surface (arrows) of atelectatic lung tissue (black asterisk). Lighter-colored normal lung tissue (white asterisk) is visible at the right.
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Figure 2a. PPSS in a 48-year-old woman with a cough. (a) Posteroanterior chest radiograph demonstrates a supra-hilar mass that extends into the right lung. (b) Contrast-enhanced CT scan (lung window) demonstrates a mass, contiguous with the mediastinal pleura, that forms acute angles with the chest wall. (c) Photograph of the gross specimen shows a well-circumscribed multicystic mass that abuts the pleura (curved arrow) and is surrounded by lung tissue. The mass is partly encapsulated and contains extensive areas of hemorrhage (straight arrow) and necrosis (arrowhead), as well as solid tumor tissue (*).
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Figure 2b. PPSS in a 48-year-old woman with a cough. (a) Posteroanterior chest radiograph demonstrates a supra-hilar mass that extends into the right lung. (b) Contrast-enhanced CT scan (lung window) demonstrates a mass, contiguous with the mediastinal pleura, that forms acute angles with the chest wall. (c) Photograph of the gross specimen shows a well-circumscribed multicystic mass that abuts the pleura (curved arrow) and is surrounded by lung tissue. The mass is partly encapsulated and contains extensive areas of hemorrhage (straight arrow) and necrosis (arrowhead), as well as solid tumor tissue (*).
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Figure 2c. PPSS in a 48-year-old woman with a cough. (a) Posteroanterior chest radiograph demonstrates a supra-hilar mass that extends into the right lung. (b) Contrast-enhanced CT scan (lung window) demonstrates a mass, contiguous with the mediastinal pleura, that forms acute angles with the chest wall. (c) Photograph of the gross specimen shows a well-circumscribed multicystic mass that abuts the pleura (curved arrow) and is surrounded by lung tissue. The mass is partly encapsulated and contains extensive areas of hemorrhage (straight arrow) and necrosis (arrowhead), as well as solid tumor tissue (*).
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Figure 3a. PPSS in a 37-year-old-man with chest pain and right arm swelling. (a) Posteroanterior radiograph of the upper chest demonstrates a right apical mass with a chest wall interface suggestive of extrapulmonary origin, and, inferior to the mass, a pleural-based nodule (arrow). (b) Contrast-enhanced CT scan demonstrates a predominantly cystic mass with an eccentrically thickened wall (*) and a metastatic nodule (arrowhead) along the lateral pleural surface. (c) Photograph of the gross specimen shows a unilocular cystic mass, resected en bloc with a section of rib (*). The inner wall of the cyst is lined with irregular masses of pink-tan tumor (arrowheads).
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Figure 3b. PPSS in a 37-year-old-man with chest pain and right arm swelling. (a) Posteroanterior radiograph of the upper chest demonstrates a right apical mass with a chest wall interface suggestive of extrapulmonary origin, and, inferior to the mass, a pleural-based nodule (arrow). (b) Contrast-enhanced CT scan demonstrates a predominantly cystic mass with an eccentrically thickened wall (*) and a metastatic nodule (arrowhead) along the lateral pleural surface. (c) Photograph of the gross specimen shows a unilocular cystic mass, resected en bloc with a section of rib (*). The inner wall of the cyst is lined with irregular masses of pink-tan tumor (arrowheads).
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Figure 3c. PPSS in a 37-year-old-man with chest pain and right arm swelling. (a) Posteroanterior radiograph of the upper chest demonstrates a right apical mass with a chest wall interface suggestive of extrapulmonary origin, and, inferior to the mass, a pleural-based nodule (arrow). (b) Contrast-enhanced CT scan demonstrates a predominantly cystic mass with an eccentrically thickened wall (*) and a metastatic nodule (arrowhead) along the lateral pleural surface. (c) Photograph of the gross specimen shows a unilocular cystic mass, resected en bloc with a section of rib (*). The inner wall of the cyst is lined with irregular masses of pink-tan tumor (arrowheads).
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Figure 4a. PPSS in a 36-year-old man with dyspnea and pleuritic chest pain. (a) Posteroanterior chest radiograph of the right lung demonstrates a right hilar mass with smooth borders. (b) Contrast-enhanced CT scan demonstrates a large, low-attenuation mass with an enhanced rim (arrowhead) and internal septa. (c) Axial unenhanced T1-weighted (repetition time msec/echo time msec, 516.7/10) MR image demonstrates marked heterogeneity not evident in b. (d) Axial T2-weighted (2110/57.6) MR image shows further contrast among internal components, with well-demarcated spaces (arrowheads) suggestive of cysts. (e) Axial gadolinium-enhanced T1-weighted (28/1.4) MR image demonstrates nodular areas of increased blood flow represented by increased signal intensity (*) compared with that in c. Enhancement of the rim (arrowhead) also is evident. (f) Photograph of the gross specimen demonstrates a well-circumscribed, partly encapsulated (straight arrow) reniform mass attached to the chest wall (curved arrow) and surrounded by lung tissue (black asterisk). Cut surface reveals marked variability of contents, with collapsed cysts (white asterisks), zones of necrosis, areas of hemorrhage, and solid tumor tissue (arrowhead).
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Figure 4b. PPSS in a 36-year-old man with dyspnea and pleuritic chest pain. (a) Posteroanterior chest radiograph of the right lung demonstrates a right hilar mass with smooth borders. (b) Contrast-enhanced CT scan demonstrates a large, low-attenuation mass with an enhanced rim (arrowhead) and internal septa. (c) Axial unenhanced T1-weighted (repetition time msec/echo time msec, 516.7/10) MR image demonstrates marked heterogeneity not evident in b. (d) Axial T2-weighted (2110/57.6) MR image shows further contrast among internal components, with well-demarcated spaces (arrowheads) suggestive of cysts. (e) Axial gadolinium-enhanced T1-weighted (28/1.4) MR image demonstrates nodular areas of increased blood flow represented by increased signal intensity (*) compared with that in c. Enhancement of the rim (arrowhead) also is evident. (f) Photograph of the gross specimen demonstrates a well-circumscribed, partly encapsulated (straight arrow) reniform mass attached to the chest wall (curved arrow) and surrounded by lung tissue (black asterisk). Cut surface reveals marked variability of contents, with collapsed cysts (white asterisks), zones of necrosis, areas of hemorrhage, and solid tumor tissue (arrowhead).
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Figure 4c. PPSS in a 36-year-old man with dyspnea and pleuritic chest pain. (a) Posteroanterior chest radiograph of the right lung demonstrates a right hilar mass with smooth borders. (b) Contrast-enhanced CT scan demonstrates a large, low-attenuation mass with an enhanced rim (arrowhead) and internal septa. (c) Axial unenhanced T1-weighted (repetition time msec/echo time msec, 516.7/10) MR image demonstrates marked heterogeneity not evident in b. (d) Axial T2-weighted (2110/57.6) MR image shows further contrast among internal components, with well-demarcated spaces (arrowheads) suggestive of cysts. (e) Axial gadolinium-enhanced T1-weighted (28/1.4) MR image demonstrates nodular areas of increased blood flow represented by increased signal intensity (*) compared with that in c. Enhancement of the rim (arrowhead) also is evident. (f) Photograph of the gross specimen demonstrates a well-circumscribed, partly encapsulated (straight arrow) reniform mass attached to the chest wall (curved arrow) and surrounded by lung tissue (black asterisk). Cut surface reveals marked variability of contents, with collapsed cysts (white asterisks), zones of necrosis, areas of hemorrhage, and solid tumor tissue (arrowhead).
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Figure 4d. PPSS in a 36-year-old man with dyspnea and pleuritic chest pain. (a) Posteroanterior chest radiograph of the right lung demonstrates a right hilar mass with smooth borders. (b) Contrast-enhanced CT scan demonstrates a large, low-attenuation mass with an enhanced rim (arrowhead) and internal septa. (c) Axial unenhanced T1-weighted (repetition time msec/echo time msec, 516.7/10) MR image demonstrates marked heterogeneity not evident in b. (d) Axial T2-weighted (2110/57.6) MR image shows further contrast among internal components, with well-demarcated spaces (arrowheads) suggestive of cysts. (e) Axial gadolinium-enhanced T1-weighted (28/1.4) MR image demonstrates nodular areas of increased blood flow represented by increased signal intensity (*) compared with that in c. Enhancement of the rim (arrowhead) also is evident. (f) Photograph of the gross specimen demonstrates a well-circumscribed, partly encapsulated (straight arrow) reniform mass attached to the chest wall (curved arrow) and surrounded by lung tissue (black asterisk). Cut surface reveals marked variability of contents, with collapsed cysts (white asterisks), zones of necrosis, areas of hemorrhage, and solid tumor tissue (arrowhead).
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Figure 4e. PPSS in a 36-year-old man with dyspnea and pleuritic chest pain. (a) Posteroanterior chest radiograph of the right lung demonstrates a right hilar mass with smooth borders. (b) Contrast-enhanced CT scan demonstrates a large, low-attenuation mass with an enhanced rim (arrowhead) and internal septa. (c) Axial unenhanced T1-weighted (repetition time msec/echo time msec, 516.7/10) MR image demonstrates marked heterogeneity not evident in b. (d) Axial T2-weighted (2110/57.6) MR image shows further contrast among internal components, with well-demarcated spaces (arrowheads) suggestive of cysts. (e) Axial gadolinium-enhanced T1-weighted (28/1.4) MR image demonstrates nodular areas of increased blood flow represented by increased signal intensity (*) compared with that in c. Enhancement of the rim (arrowhead) also is evident. (f) Photograph of the gross specimen demonstrates a well-circumscribed, partly encapsulated (straight arrow) reniform mass attached to the chest wall (curved arrow) and surrounded by lung tissue (black asterisk). Cut surface reveals marked variability of contents, with collapsed cysts (white asterisks), zones of necrosis, areas of hemorrhage, and solid tumor tissue (arrowhead).
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Figure 4f. PPSS in a 36-year-old man with dyspnea and pleuritic chest pain. (a) Posteroanterior chest radiograph of the right lung demonstrates a right hilar mass with smooth borders. (b) Contrast-enhanced CT scan demonstrates a large, low-attenuation mass with an enhanced rim (arrowhead) and internal septa. (c) Axial unenhanced T1-weighted (repetition time msec/echo time msec, 516.7/10) MR image demonstrates marked heterogeneity not evident in b. (d) Axial T2-weighted (2110/57.6) MR image shows further contrast among internal components, with well-demarcated spaces (arrowheads) suggestive of cysts. (e) Axial gadolinium-enhanced T1-weighted (28/1.4) MR image demonstrates nodular areas of increased blood flow represented by increased signal intensity (*) compared with that in c. Enhancement of the rim (arrowhead) also is evident. (f) Photograph of the gross specimen demonstrates a well-circumscribed, partly encapsulated (straight arrow) reniform mass attached to the chest wall (curved arrow) and surrounded by lung tissue (black asterisk). Cut surface reveals marked variability of contents, with collapsed cysts (white asterisks), zones of necrosis, areas of hemorrhage, and solid tumor tissue (arrowhead).
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Figure 5a. PPSS in a 29-year-old man with pleuritic pain. (a) Posteroanterior chest radiograph of the left lung demonstrates a suprahilar mass with smooth borders. (b) Contrast-enhanced CT scan shows a homogeneous mass that abuts the left main pulmonary artery. (c) Axial T2-weighted (2666/90.8) MR image depicts a mass with mild heterogeneity, signal intensity slightly higher than that of muscle, and a rim of higher signal intensity that conforms to the major fissure (arrowhead). (d) Axial gadolinium-enhanced T1-weighted (150/4.2) MR image demonstrates a curvilinear peripheral area of striking enhancement (arrow) that correlates with the capsule. (e) Photograph of the gross specimen shows a well-circumscribed mass partly surrounded by a fibrous capsule (curved arrow). Cut surface reveals variable contents including cysts, some of which contain blood (*). Areas of solid tumor vary in color from yellow-tan to pink and contain foci of hemorrhage (arrowhead) and necrosis (straight arrow). The surrounding lung tissue is inked black. (f) Low-power photomicrograph (original magnification, x100; H-E stain) reveals a bandlike arrangement of vascular spaces (arrowheads) at the interface of the capsule (curved arrow) and viable tumor (straight arrow); tumor necrosis also is present (*).
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Figure 5b. PPSS in a 29-year-old man with pleuritic pain. (a) Posteroanterior chest radiograph of the left lung demonstrates a suprahilar mass with smooth borders. (b) Contrast-enhanced CT scan shows a homogeneous mass that abuts the left main pulmonary artery. (c) Axial T2-weighted (2666/90.8) MR image depicts a mass with mild heterogeneity, signal intensity slightly higher than that of muscle, and a rim of higher signal intensity that conforms to the major fissure (arrowhead). (d) Axial gadolinium-enhanced T1-weighted (150/4.2) MR image demonstrates a curvilinear peripheral area of striking enhancement (arrow) that correlates with the capsule. (e) Photograph of the gross specimen shows a well-circumscribed mass partly surrounded by a fibrous capsule (curved arrow). Cut surface reveals variable contents including cysts, some of which contain blood (*). Areas of solid tumor vary in color from yellow-tan to pink and contain foci of hemorrhage (arrowhead) and necrosis (straight arrow). The surrounding lung tissue is inked black. (f) Low-power photomicrograph (original magnification, x100; H-E stain) reveals a bandlike arrangement of vascular spaces (arrowheads) at the interface of the capsule (curved arrow) and viable tumor (straight arrow); tumor necrosis also is present (*).
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Figure 5c. PPSS in a 29-year-old man with pleuritic pain. (a) Posteroanterior chest radiograph of the left lung demonstrates a suprahilar mass with smooth borders. (b) Contrast-enhanced CT scan shows a homogeneous mass that abuts the left main pulmonary artery. (c) Axial T2-weighted (2666/90.8) MR image depicts a mass with mild heterogeneity, signal intensity slightly higher than that of muscle, and a rim of higher signal intensity that conforms to the major fissure (arrowhead). (d) Axial gadolinium-enhanced T1-weighted (150/4.2) MR image demonstrates a curvilinear peripheral area of striking enhancement (arrow) that correlates with the capsule. (e) Photograph of the gross specimen shows a well-circumscribed mass partly surrounded by a fibrous capsule (curved arrow). Cut surface reveals variable contents including cysts, some of which contain blood (*). Areas of solid tumor vary in color from yellow-tan to pink and contain foci of hemorrhage (arrowhead) and necrosis (straight arrow). The surrounding lung tissue is inked black. (f) Low-power photomicrograph (original magnification, x100; H-E stain) reveals a bandlike arrangement of vascular spaces (arrowheads) at the interface of the capsule (curved arrow) and viable tumor (straight arrow); tumor necrosis also is present (*).
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Figure 5d. PPSS in a 29-year-old man with pleuritic pain. (a) Posteroanterior chest radiograph of the left lung demonstrates a suprahilar mass with smooth borders. (b) Contrast-enhanced CT scan shows a homogeneous mass that abuts the left main pulmonary artery. (c) Axial T2-weighted (2666/90.8) MR image depicts a mass with mild heterogeneity, signal intensity slightly higher than that of muscle, and a rim of higher signal intensity that conforms to the major fissure (arrowhead). (d) Axial gadolinium-enhanced T1-weighted (150/4.2) MR image demonstrates a curvilinear peripheral area of striking enhancement (arrow) that correlates with the capsule. (e) Photograph of the gross specimen shows a well-circumscribed mass partly surrounded by a fibrous capsule (curved arrow). Cut surface reveals variable contents including cysts, some of which contain blood (*). Areas of solid tumor vary in color from yellow-tan to pink and contain foci of hemorrhage (arrowhead) and necrosis (straight arrow). The surrounding lung tissue is inked black. (f) Low-power photomicrograph (original magnification, x100; H-E stain) reveals a bandlike arrangement of vascular spaces (arrowheads) at the interface of the capsule (curved arrow) and viable tumor (straight arrow); tumor necrosis also is present (*).
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Figure 5e. PPSS in a 29-year-old man with pleuritic pain. (a) Posteroanterior chest radiograph of the left lung demonstrates a suprahilar mass with smooth borders. (b) Contrast-enhanced CT scan shows a homogeneous mass that abuts the left main pulmonary artery. (c) Axial T2-weighted (2666/90.8) MR image depicts a mass with mild heterogeneity, signal intensity slightly higher than that of muscle, and a rim of higher signal intensity that conforms to the major fissure (arrowhead). (d) Axial gadolinium-enhanced T1-weighted (150/4.2) MR image demonstrates a curvilinear peripheral area of striking enhancement (arrow) that correlates with the capsule. (e) Photograph of the gross specimen shows a well-circumscribed mass partly surrounded by a fibrous capsule (curved arrow). Cut surface reveals variable contents including cysts, some of which contain blood (*). Areas of solid tumor vary in color from yellow-tan to pink and contain foci of hemorrhage (arrowhead) and necrosis (straight arrow). The surrounding lung tissue is inked black. (f) Low-power photomicrograph (original magnification, x100; H-E stain) reveals a bandlike arrangement of vascular spaces (arrowheads) at the interface of the capsule (curved arrow) and viable tumor (straight arrow); tumor necrosis also is present (*).
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Figure 5f. PPSS in a 29-year-old man with pleuritic pain. (a) Posteroanterior chest radiograph of the left lung demonstrates a suprahilar mass with smooth borders. (b) Contrast-enhanced CT scan shows a homogeneous mass that abuts the left main pulmonary artery. (c) Axial T2-weighted (2666/90.8) MR image depicts a mass with mild heterogeneity, signal intensity slightly higher than that of muscle, and a rim of higher signal intensity that conforms to the major fissure (arrowhead). (d) Axial gadolinium-enhanced T1-weighted (150/4.2) MR image demonstrates a curvilinear peripheral area of striking enhancement (arrow) that correlates with the capsule. (e) Photograph of the gross specimen shows a well-circumscribed mass partly surrounded by a fibrous capsule (curved arrow). Cut surface reveals variable contents including cysts, some of which contain blood (*). Areas of solid tumor vary in color from yellow-tan to pink and contain foci of hemorrhage (arrowhead) and necrosis (straight arrow). The surrounding lung tissue is inked black. (f) Low-power photomicrograph (original magnification, x100; H-E stain) reveals a bandlike arrangement of vascular spaces (arrowheads) at the interface of the capsule (curved arrow) and viable tumor (straight arrow); tumor necrosis also is present (*).
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Figure 6a. PPSS in a 42-year-old woman with dyspnea. (a) Posteroanterior chest radiograph demonstrates an opacified left hemithorax with rightward shift of the mediastinum. (b) Coronal CT image reconstructed from axial CT data shows a large heterogeneous mass (*) that fills the upper left hemithorax; a large pleural effusion; and a pleural-based metastasis on the diaphragmatic surface (arrow).
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Figure 6b. PPSS in a 42-year-old woman with dyspnea. (a) Posteroanterior chest radiograph demonstrates an opacified left hemithorax with rightward shift of the mediastinum. (b) Coronal CT image reconstructed from axial CT data shows a large heterogeneous mass (*) that fills the upper left hemithorax; a large pleural effusion; and a pleural-based metastasis on the diaphragmatic surface (arrow).
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On CT images, the majority of lesions (eight of 11) appeared to be pleural-based, in either peripheral or parafissural locations (Figs 7a, 8a). However, localization of the mass to either the lung or the pleura was uncertain in the remaining three of 11 cases, in which the mass merged at an acute angle with the pleural surface (Figs 1b, 2b, 3b). The maximum diameters of the tumors ranged from 5 to 20 cm (mean, 10 cm). In almost all cases (nine of 11), the mass was enhanced heterogeneously and comprised nodular soft-tissue components mixed with areas of low attenuation and, occasionally, septa; in many cases, an enhanced thin peripheral rim was evident (Figs 1b, 3b, 4b, 6b, 7a). In two of 11 cases, the mass was mildly and homogeneously enhanced and demonstrated attenuation slightly lower than that of the chest wall musculature. In the majority of cases (seven of 11), an ipsilateral pleural effusion was evident (Figs 6b, 8a). Enhanced vessels were visualized within one tumor (Fig 9a). One patient had an associated smooth sclerotic rib abnormality, but there was no evidence of bone destruction or chest wall invasion in any case. In two cases, pleural-based nodules were evident that later proved to be metastases (Figs 3b, 6b). There was no evidence of tumor calcification, lung metastasis, or lymphadenopathy. PET/CT images in one case demonstrated focal increased uptake of FDG (maximum standardized uptake value, 7.0) in the lesion (Fig 9b).
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Figure 7a. PPSS in a 21-year-old man with right-sided chest pain. (a) Contrast-enhanced CT scan demonstrates a multilobular, heterogeneous, pleural-based mass. (b) Photograph of the gross specimen demonstrates a bosselated solid tan mass that is partly encapsulated and that adheres to an adjacent rib (*). (c) Low-power photomicrograph (original magnification, x100; H-E stain) shows an interface of eosinophilic protein-aceous cyst contents (*) and viable tumor cells. (d) Low-power photomicrograph (original magnification, x100; H-E stain) shows an interface of zones of myxoid change (*) and tumor cells (arrowhead), with more prominent vascularity (arrow) in the latter. (e) Low-power photomicrograph (original magnification, x100; H-E stain) shows an interface (arrowheads) between fascicles of tumor cells (*) oriented in different planes. These distinct tissue interfaces offer a possible explanation for the heterogeneous imaging features.
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Figure 7b. PPSS in a 21-year-old man with right-sided chest pain. (a) Contrast-enhanced CT scan demonstrates a multilobular, heterogeneous, pleural-based mass. (b) Photograph of the gross specimen demonstrates a bosselated solid tan mass that is partly encapsulated and that adheres to an adjacent rib (*). (c) Low-power photomicrograph (original magnification, x100; H-E stain) shows an interface of eosinophilic protein-aceous cyst contents (*) and viable tumor cells. (d) Low-power photomicrograph (original magnification, x100; H-E stain) shows an interface of zones of myxoid change (*) and tumor cells (arrowhead), with more prominent vascularity (arrow) in the latter. (e) Low-power photomicrograph (original magnification, x100; H-E stain) shows an interface (arrowheads) between fascicles of tumor cells (*) oriented in different planes. These distinct tissue interfaces offer a possible explanation for the heterogeneous imaging features.
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Figure 7c. PPSS in a 21-year-old man with right-sided chest pain. (a) Contrast-enhanced CT scan demonstrates a multilobular, heterogeneous, pleural-based mass. (b) Photograph of the gross specimen demonstrates a bosselated solid tan mass that is partly encapsulated and that adheres to an adjacent rib (*). (c) Low-power photomicrograph (original magnification, x100; H-E stain) shows an interface of eosinophilic protein-aceous cyst contents (*) and viable tumor cells. (d) Low-power photomicrograph (original magnification, x100; H-E stain) shows an interface of zones of myxoid change (*) and tumor cells (arrowhead), with more prominent vascularity (arrow) in the latter. (e) Low-power photomicrograph (original magnification, x100; H-E stain) shows an interface (arrowheads) between fascicles of tumor cells (*) oriented in different planes. These distinct tissue interfaces offer a possible explanation for the heterogeneous imaging features.
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Figure 7d. PPSS in a 21-year-old man with right-sided chest pain. (a) Contrast-enhanced CT scan demonstrates a multilobular, heterogeneous, pleural-based mass. (b) Photograph of the gross specimen demonstrates a bosselated solid tan mass that is partly encapsulated and that adheres to an adjacent rib (*). (c) Low-power photomicrograph (original magnification, x100; H-E stain) shows an interface of eosinophilic protein-aceous cyst contents (*) and viable tumor cells. (d) Low-power photomicrograph (original magnification, x100; H-E stain) shows an interface of zones of myxoid change (*) and tumor cells (arrowhead), with more prominent vascularity (arrow) in the latter. (e) Low-power photomicrograph (original magnification, x100; H-E stain) shows an interface (arrowheads) between fascicles of tumor cells (*) oriented in different planes. These distinct tissue interfaces offer a possible explanation for the heterogeneous imaging features.
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Figure 7e. PPSS in a 21-year-old man with right-sided chest pain. (a) Contrast-enhanced CT scan demonstrates a multilobular, heterogeneous, pleural-based mass. (b) Photograph of the gross specimen demonstrates a bosselated solid tan mass that is partly encapsulated and that adheres to an adjacent rib (*). (c) Low-power photomicrograph (original magnification, x100; H-E stain) shows an interface of eosinophilic protein-aceous cyst contents (*) and viable tumor cells. (d) Low-power photomicrograph (original magnification, x100; H-E stain) shows an interface of zones of myxoid change (*) and tumor cells (arrowhead), with more prominent vascularity (arrow) in the latter. (e) Low-power photomicrograph (original magnification, x100; H-E stain) shows an interface (arrowheads) between fascicles of tumor cells (*) oriented in different planes. These distinct tissue interfaces offer a possible explanation for the heterogeneous imaging features.
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Figure 8a. PPSS in a 46-year-old woman with right shoulder pain. (a) Contrast-enhanced CT scan demonstrates a homogeneous pleural-based mass and a small pleural effusion. (b) Axial T2-weighted (2379/92.5) MR image shows the same mass with predominantly intermediate signal intensity and high-signal-intensity foci. The pleural effusion also demonstrates high signal intensity. (c) Axial gadolinium-enhanced T1-weighted (140/4.2) MR image shows an enhanced rim (arrowhead).
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Figure 8b. PPSS in a 46-year-old woman with right shoulder pain. (a) Contrast-enhanced CT scan demonstrates a homogeneous pleural-based mass and a small pleural effusion. (b) Axial T2-weighted (2379/92.5) MR image shows the same mass with predominantly intermediate signal intensity and high-signal-intensity foci. The pleural effusion also demonstrates high signal intensity. (c) Axial gadolinium-enhanced T1-weighted (140/4.2) MR image shows an enhanced rim (arrowhead).
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Figure 8c. PPSS in a 46-year-old woman with right shoulder pain. (a) Contrast-enhanced CT scan demonstrates a homogeneous pleural-based mass and a small pleural effusion. (b) Axial T2-weighted (2379/92.5) MR image shows the same mass with predominantly intermediate signal intensity and high-signal-intensity foci. The pleural effusion also demonstrates high signal intensity. (c) Axial gadolinium-enhanced T1-weighted (140/4.2) MR image shows an enhanced rim (arrowhead).
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Figure 9a. PPSS in a 27-year-old woman with a recent onset of dyspnea. (a) Contrast-enhanced CT scan depicts marked heterogeneity, with enhanced linear structures consistent with vessels (arrowheads) and surrounding collapsed lung (*). (b) Axial PET/CT fusion image shows increased FDG uptake in the mass, with a maximum standardized uptake value of 7.0. (c) Photograph of the gross specimen shows a well-circumscribed encapsulated mass bordered by lung tissue (*). The cut surface is variegated tan-white with focal areas of hemorrhage (arrow) and prominent vessels (arrowhead).
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Figure 9b. PPSS in a 27-year-old woman with a recent onset of dyspnea. (a) Contrast-enhanced CT scan depicts marked heterogeneity, with enhanced linear structures consistent with vessels (arrowheads) and surrounding collapsed lung (*). (b) Axial PET/CT fusion image shows increased FDG uptake in the mass, with a maximum standardized uptake value of 7.0. (c) Photograph of the gross specimen shows a well-circumscribed encapsulated mass bordered by lung tissue (*). The cut surface is variegated tan-white with focal areas of hemorrhage (arrow) and prominent vessels (arrowhead).
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Figure 9c. PPSS in a 27-year-old woman with a recent onset of dyspnea. (a) Contrast-enhanced CT scan depicts marked heterogeneity, with enhanced linear structures consistent with vessels (arrowheads) and surrounding collapsed lung (*). (b) Axial PET/CT fusion image shows increased FDG uptake in the mass, with a maximum standardized uptake value of 7.0. (c) Photograph of the gross specimen shows a well-circumscribed encapsulated mass bordered by lung tissue (*). The cut surface is variegated tan-white with focal areas of hemorrhage (arrow) and prominent vessels (arrowhead).
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T1-weighted and T2-weighted MR images showed a well-circumscribed mass without evidence of spiculation or satellite nodules in all cases (three of three patients). In two cases, the T1-weighted MR images demonstrated a lesion with internally heterogeneous intermediate signal intensity similar to that of the chest wall musculature. The findings on T2-weighted images in these two cases included nodular areas of intermediate signal intensity combined with punctate or cystic areas of high signal intensity suggestive of necrosis, hemorrhage, or myxoid material (Figs 4c–4e, 5c). In the third case, the T1-weighted images showed a more homogeneous mass with signal that was isointense to that of the chest wall musculature, and the corresponding T2-weighted images showed less heterogeneity than was present in the other two cases (Fig 8b). In all three cases, MR images obtained after the administration of gadopentetate dimeglumine demonstrated a peripheral rim of enhancement in the lesion (Figs 4e, 5d, 8c). Ipsilateral pleural effusion was evident in two of the three cases (Fig 8b). It is noteworthy that CT images in two cases demonstrated a homogeneous mass, while the corresponding MR images showed remarkably heterogeneous signal intensity within the tumor (Figs 5, 8).
Findings in Gross Specimens
In most cases (10 of 12), the tumor contained a variety of necrotic, hemorrhagic, cystic, and friable components (Figs 2c, 3c, 4f, 5e, 9c). Five of these 10 lesions had distinctly nodular soft-tissue components (Fig 3c). Two cases consisted of uniform solid soft tissue (Fig 7b). In six of 12 cases, the tumor was encased within a grossly visible capsule, which was variously described in the records as a "peel," "pseudocapsule," "outer fibrous wall delaminating membrane," or "thin fibroconnective tissue layer" (Figs 2c, 4f, 5e, 7b, 9c). Pleural adhesions were identified by either the surgeon or the pathologist in seven of 12 cases (Figs 1c, 3c, 4f, 7b); at histologic examination, adhesions in three of the seven cases represented chronic inflammation without evidence of tumor involvement. Atelectatic lung tissue adjacent to the mass in three of 12 cases was described (Fig 1c). Grossly visible calcifications within the mass in one case were documented.
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General Overview
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Clinical Manifestations
In the four notable studies of PPSS cases published since 1995 (n = 5–25), the mean ages of the patients ranged from 25 to 39 years (overall age range, 9–77 years) (7,8,13,14). No difference in the frequency of PPSS according to sex was found in any of these studies. The demographic characteristics of patients with PPSS closely match those of patients with extrathoracic synovial sarcomas (4,5). Typical signs and symptoms include chest pain (24%–80%), dyspnea (8%–36%), cough (8%–33%), and hemoptysis (20%–25%). In the largest patient series, 40% of patients were asymptomatic, and PPSS was an incidental finding at chest radiography (8). Dysphagia, pleuritic pain, chest heaviness, shoulder pain, and fever were additional reported symptoms but occurred much less frequently. One patient presented with spontaneous pneumothorax; two had abrupt-onset or recurrent hemothorax (7,13,15). In the only series for which the duration of symptoms was recorded, the period ranged widely, from 1 week to 10 years (13). PPSS may metastasize to bone, liver, skin, the central nervous system, and even breast tissue (8,16).
Pathologic Features
Synovial sarcoma is a mesenchymal spindle cell tumor characterized by variable epithelial differentiation and the specific chromosomal translocation t(X;18)(p11.2;q11.2). In the 2002 World Health Organization classification of tumors of soft tissue and bone, synovial sarcoma is classified as a malignant soft-tissue tumor of uncertain differentiation (17). Classification of this group of tumors is based on a line of differentiation that is determined by gene expression, and there is little evidence for the origin of these tumors in their normal cellular counterparts (17). Historically, synovial sarcomas were thought to be associated with synovium, and the epithelial component was believed to simulate synovial slits (4). However, the neoplasms have no demonstrable relationship to synovial tissue, and the name is thus a misnomer (18). The histogenesis of synovial sarcomas is not yet known, but their origin is postulated to be in a totipotential mesenchymal cell that is capable of epithelial differentiation (18–21).
The gross, histopathologic, immunohistochemical, and ultrastructural features of primary intrathoracic synovial sarcoma are identical to those of sarcomas in soft-tissue sites (8,13). At gross inspection, intrathoracic tumors vary broadly in size, with diameters ranging from 0.6 to 21 cm (7,8). Most tumors appear well circumscribed, and they may be either unencapsulated (Fig 10) or surrounded by a thin fibrous capsule (Fig 11) (7,9). Sectioning of excised specimens reveals tan-white cut surfaces that vary in texture from soft and fleshy to firm and rubbery. Necrosis, hemorrhage, and cystic change are common (Fig 12). Gross calcification may be evident (7).
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Figure 10. Unencapsulated PPSS. Low-power photomicrograph (original magnification, x100; H-E stain) shows a tumor (*) with a well-demarcated expansile border (arrowheads) that mildly compresses adjacent alveoli. There is no capsule between the tumor and lung tissue.
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Figure 11. Encapsulated PPSS. Medium-power photomicrograph (original magnification, x200; H-E stain) shows a thick fibrous capsule (between arrowheads) that borders viable tumor tissue (*).
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Figure 12. Heterogeneity of PPSS. Low-power photomicrograph (original magnification, x 100; H-E stain) shows areas of myxoid change (curved arrow), densely cellular tumor tissue (straight arrow), cystic spaces (*), and hemorrhage with necrosis (arrowhead).
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Synovial sarcoma encompasses two histologic subtypes, monophasic and biphasic, with the monophasic variant being the more common. The presence of poorly differentiated tumor cells within lesions of either subtype is considered indicative of a poorer prognosis (4). Monophasic synovial sarcoma is composed of relatively uniform spindle cells with elongated nuclei, slightly basophilic cytoplasm, and indistinct cell borders. Interlacing fascicles of tumor cells may be densely packed, with little intervening stroma, or may be embedded in a variable background of myxoid to densely collagenous elements (Fig 13).
Biphasic synovial sarcoma is composed of spindle cells and epithelial components (Fig 14). The spindle cell component is similar to that in monophasic tumors. The epithelial component may be arranged in well-formed glandular structures or solid sheets. The proportions of the spindle cell and epithelial components vary widely. If histologic sampling is inadequate, the epithelial component may be overlooked entirely and the lesion may be classified as monophasic. Conversely, entrapped pulmonary epithelium is easily mistaken for the epithelial component of a biphasic tumor. Immunohistochemical analysis performed with the use of antibodies to thyroid transcription factor 1 to stain pneumocytes can help avoid this pitfall. This type of analysis is often undertaken to confirm the diagnosis of synovial sarcoma. Tumors are typically positive for pancytokeratin, cytokeratin 7, and epithelial membrane antigen, with more intense staining of epithelial components than of spindle cells.
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Figure 14. Biphasic PPSS. High-power photomicrograph (original magnification, x400; H-E stain) demonstrates the epithelial (left) and spindle cell (right) components characteristic of this tumor.
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Synovial sarcoma is characterized cytogenetically by a t(X;18)(p11.2;q11.2) translocation that results in fusion of the SYT gene on chromosome 18 with the SSX1 or SSX2 gene on chromosome X. Both epithelial and spindle cells carry the translocation (22). The SYT-SSX1 fusion is present in the majority of biphasic tumors, while SYT-SSX1 and SYT-SSX2 fusions are seen with equal frequency in tumors of the monophasic subtype (23). This distinctive chromosomal translocation is present in 80%–90% of synovial sarcomas regardless of subtype, and it appears to be specific (17,20,24,25).
Biphasic synovial sarcomas may be relatively easy to identify at light microscopy, but their differentiation from other biphasic tumors, including diffuse biphasic malignant mesothelioma, pleomorphic carcinoma of the lung, and pleuropulmonary blastoma, is essential. Solitary fibrous tumor, spindle cell carcinoma of the lung, diffuse sarcomatoid malignant mesothelioma, fibrosarcoma, leiomyosarcoma, cellular schwannoma, malignant peripheral nerve sheath tumor, and Ewing sarcoma enter into the differential diagnosis of monophasic synovial sarcoma. Separation of these entities is based on clinical history, radiologic distribution of disease, histologic features, histochemical and immunohistochemical staining, and cytogenetic and molecular studies (14,24).
While it is important to be aware of synovial sarcoma as a possible primary intrathoracic malignancy, primary synovial sarcomas in the lungs, pleura, and mediastinum are rare (1,26). In comparison, the occurrence of synovial sarcoma as an extrathoracic soft-tissue primary tumor is relatively common, and distant metastases develop in 40%–50% of patients; the lung is the most common metastatic site, and massive pleuropulmonary metastases are the leading cause of death (4). Thus, the most important entity in the differential diagnosis is metastatic synovial sarcoma. Because the morphologic features of primary and metastatic synovial sarcomas are similar, clinical and radiologic evaluation is essential to exclude the presence of a primary tumor outside the thorax.
Radiologic Features
The radiologic manifestations of PPSS have been described over the past decade in histopathologic and surgical review articles, case reports, and a recent review article. There is no propensity for sidedness; PPSS occurs with nearly equal frequency in either hemithorax (7,8,13,27). On chest radiographs, PPSS may be depicted as a pulmonary parenchymal consolidation or mass (with either sharp or ill-defined margins), a pleural-based mass, focal pleural thickening with or without a central mass, or near-complete opacification of a hemithorax (7,14,15,24,27–30). The contralateral lung appears normal, although mediastinal shift may occur in the presence of a very large mass (7). An ipsilateral pleural effusion is often evident (7,14,15,24,29). Rarely, chest radiographs reveal pneumothorax (14). Only in one case report was the radiographic depiction of tumor calcification noted (7). To our knowledge, neither lymphadenopathy nor cavitation has been observed at chest radiography.
At CT, PPSS typically is manifested as a well-defined, heterogeneously enhanced mass that contains areas of fluid attenuation compatible with necrosis or hemorrhage (7,24,27). Although a lesion may appear to be located primarily within the lung or the pleura, the site of origin is often unclear (7,14,15,27,29). An ipsilateral pleural effusion is often present and may represent acute or recurrent hemothorax (13–15,24,27). A rim of ground-glass opacity surrounding the mass has been reported (30). There is one reported case of enlarged diaphragmatic lymph nodes, and another of mediastinal lymphadenopathy (12,27). Synovial sarcomas that arise in the chest wall demonstrate well-defined margins and heterogeneous enhancement as well as cortical bone destruction, tumor calcifications, and tumor infiltration of the chest wall musculature at CT (31–33).
MR imaging findings of PPSS have been described chiefly in cases of primary chest wall masses. A synovial sarcoma that arises in the chest wall usually demonstrates internal heterogeneity, with predominantly intermediate signal intensity (isointense to the signal in the chest wall musculature)
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