Primary Pulmonary Synovial Sarcoma in a Tertiary Referral Center: Clinical Characteristics, CT, and 18F-FDG PET Findings, With Pathologic Correlations

Abstract

The purpose of this study was to describe the patient characteristics, computed tomography (CT) and F-fluorodeoxyglucose positron emission tomography (FDG PET) findings, and clinical outcomes of primary pulmonary synovial sarcoma (PPSS), together with their pathologic correlations. The medical records of 14 patients with pathologically proven PPSS in a tertiary hospital from January 1997 to December 2014 were retrospectively reviewed. The CT findings were evaluated. The maximum standardized uptake value (maxSUV) of the tumors was obtained, and clinical outcomes with respect to tumor recurrence and mortality were assessed by Kaplan-Meier analysis. The median tumor size was 10.2 cm and the most common anatomic location was the lung followed by the pleura/chest wall and mediastinum. Most of the tumors appeared as single lesions and had circumscribed margins. All the cases showed heterogeneous enhancement with necrotic or cystic portions, and intratumoral vessels were frequently seen. Half of the tumors had intratumoral calcifications, and tumor rupture, pleural/chest wall extension, and pleural effusion occurred frequently. However, lymph node enlargement was rare. The median maxSUV of the tumors was 4.35. Patient outcomes with respect to tumor recurrence (n = 8, 57.1%) and death (n = 3, 21.4%) were poor despite their young age, and the mean follow-up period was 28.5 months.In conclusion, PPSS usually occurs in young adults, generally in the lung, presents as a large, circumscribed mass, and tumor rupture or extension of the pleura/chest wall may occur. The tumors often contain calcifications and vessels; they may exhibit triple attenuation on enhanced CT images, and clinical outcomes are poor.

FIGURE 1

Flow diagram for selecting cases of primary pulmonary synovial sarcoma.

FIGURE 2

Disease-free survival for tumor recurrence or mortality analyzed by the Kaplan–Meier method; 1 and 2-year disease-free survival rates were 50% and 35.7%, respectively.

FIGURE 3

Computed tomography (CT) images obtained in a 58-year-old woman with monophasic primary pulmonary synovial sarcoma. (A and B) Conventional transverse mediastinal CT image (5-mm thick) obtained at the level of the left pulmonary vein, and coronal mediastinal CT image (5-mm thick) obtained at the level of the left upper pulmonary vein. CT images show a 7.7-cm-sized heterogenously enhancing mass in the left lower lobe with circumscribed margin and internal cystic or necrotic portion, and an intratumoral vessel (white arrows in A and B). Note the obliterated tumor margin (black arrow in A) and pleural effusion, indicating rupture of the tumor. FDG PET reveals an FDG-avid lung mass with a maxSUV of 3.8 (not shown). (C) Pneumonectomy was performed and the photograph shows the creamy white and soft solid portion with focal hemorrhage. The cystic portion is filled with a blood clot (arrowheads). (D) On histologic analysis, (a) the periphery of the tumor shows cystic change (★); (b) a thick-walled blood vessel is present in the center of the tumor; (c) the tumor has elevated cellularity and is composed of short spindle-shaped cells with hyperchromatic nuclei, and high mitotic activity (hematoxylin–eosin stain, original magnifications 12.5, ×100, ×400, respectively); and (d) the tumor cells are positive for vimentin by immunohistochemistry. FDG PET = ¹⁸F-fluorodeoxyglucose positron emission tomography, maxSUV = maximum standardized uptake value.

FIGURE 4

Computed tomography (CT) images obtained in a 35-year-old man with monophasic primary pulmonary synovial sarcoma. (A) Nonenhanced conventional transverse mediastinal CT image (3-mm thick) obtained at the level of the bronchus intermedius. The CT image shows amorphous calcification (black arrow in A) in the right middle lobe. (B and C) Contrast-enhanced conventional transverse mediastinal CT images (3-mm thick) obtained at the level of left atrial roof and at the level of inferior vena cava. The CT images reveal a 13.2-cm heterogenously enhancing mass with an internally cystic or necrotic portion, and an intratumoral vessel. Note the enhancing pleural-based nodule in the right lower hemithorax (black arrow in B), suggestive of ipsilateral pleural metastasis, and the tumor rupture with fluid effusion with high attenuation in the pleural space, indicating hemothorax. The CT image shows a heterogenously enhancing mass with an intratumoral vessel in the left lower lobe, and another small enhancing nodule (white arrows in C), suggestive of contralateral lung metastases. FDG PET shows an FDG-avid lung mass with a maxSUV of 3.7 (not shown). (D) Pathology after core-needle biopsy shows a cellular mass with spindle-shaped cells with hyperchromatic nuclei (hematoxylin–eosin stain, original magnification ×200). (E) The tumor cells are weakly diffusely positive for Bcl-2 by immunohistochemistry, supporting the diagnosis of synovial sarcoma (original magnification ×200). (F) The tumor cells are positive for CD99 by immunohistochemistry, supporting the diagnosis of synovial sarcoma (original magnification ×200). Bcl-2 = B-cell lymphoma-2, FDG PET = ¹⁸F-fluorodeoxyglucose positron emission tomography, maxSUV = maximum standardized uptake value.

FIGURE 5

Computed tomography (CT) images obtained in a 33-year-old woman with monophasic primary pulmonary synovial sarcoma in the mediastinum. (A and B) Conventional transverse mediastinal CT image (5-mm thick) obtained at the level of the upper trachea, and coronal mediastinal CT image (5-mm thick) obtained at the level of the superior vena cava. CT images show a 12.8-cm heterogenously enhancing mass with lobulated margin and an internal cystic or necrotic portion that extends to the thoracic inlet. Chest wall invasion (white arrow in A) and pleural effusion are evident. Note the punctate calcification (black arrow in A) and intratumoral vessel (white arrow in B). FDG PET shows an FDG-avid mediastinal mass with a maxSUV of 4.9 (not shown). (C) Incomplete wide resection was performed because of severe adhesion with the left innominate vein and chest wall. The photograph shows the cut surface of the mass with a multifocal hemorrhage. (D) On histopathologic analysis, (a) the tumor (T) invades the pleural wall (black arrow); (b) it shows cystic change with hemorrhage (★); (c) a 1-mm-diameter blood vessel can be seen in the tumor; and (d) the tumor contains hypercellular short spindle-shaped cells with high mitotic activity (white arrows) (hematoxylin–eosin stain, original magnification ×12.5, ×12.5, ×100, ×400, respectively). FDG PET = ¹⁸F-fluorodeoxyglucose positron emission tomography, maxSUV = maximum standardized uptake value.