Primary Synovial Sarcoma of the Lung

Abstract

We describe a case of primary pulmonary synovial sarcoma. A 19-year-old man presented with low-grade fever, dyspnea, chest pain and left arm numbness. Chest radiographs revealed a large, well-circumscribed left perihilar mass and a small ipsilateral pleural effusion. Chest computed tomography (CT) revealed a large well-defined, heterogeneous lung mass. Magnetic resonance imaging (MRI) demonstrated a mass of heterogeneous signal intensity on T1-weighted and proton density images, and high signal intensity on short tau inversion recovery (STIR) images. Whole-body bone scintigraphy showed no evidence of skeletal involvement. Abdominal and pelvic CT showed no intra-abominal or pelvic metastases. A CT-guided biopsy provided the diagnosis of monophasic synovial sarcoma. Following four cycles of chemotherapy, integrated F-18 fluorodeoxyglucose positron emission tomography-computed tomography (18F FDG PET/CT) was performed, which demonstrated interval decrease in the size of the lesion and no significant metabolic activity. Surgical resection was then undertaken. Microscopically, the lesion was a high-grade spindle cell sarcoma consistent with monophasic synovial sarcoma. A variant X;18 translocation was identified by cytogenetic analysis and confirmed with metaphase in situ hybridization. The imaging and pathological features of this rare lesion are reviewed.

Keywords: CT, computed tomography.

Figure 1

19-year-old man with primary synovial sarcoma of the lung. AP chest radiograph shows a large well circumscribed mass in the left mid lung and a small left pleural effusion.

Figure 2

19-year-old man with primary synovial sarcoma of the lung. A, B, Contrast-enhanced chest CT (mediastinal window) shows a well circumscribed heterogeneous left lung mass abutting the left hilum and pericardium. The lesion exhibited soft tissue and low attenuation components, the latter with fluid-fluid levels consistent with cystic change.

Figure 3

19-year-old man with primary synovial sarcoma of the lung. A, Axial, and B, coronal, double inversion recovery magnetic resonance images through the lesion demonstrate a heterogeneous mass in the left mid lung that abuts the ipsilateral hilum and displaces the hilar structures.

Figure 3

19-year-old man with primary synovial sarcoma of the lung. C, Axial, and D, coronal, contrast-enhanced fast gradient echo sequences through the lesion demonstrate heterogeneous signal with medially located nodular enhancement and enhancing tissue septa and areas of low signal intensity that correlated with the cystic changes observed on CT.

Figure 4

19-year-old man with primary synovial sarcoma of the lung. F-18 FDG PET/CT fused image following chemotherapy shows interval decrease in the size of the mass, decreasing mass effect on the adjacent hilum and very little metabolic activity (SUV of 1.3).

Figure 5

19-year-old man with primary synovial sarcoma of the lung. Photomicrograph (Hematoxylin and Eosin stain; original magnification 200 power) demonstrates a tumor composed of fascicles of monotonous atypical spindle cells with scattered mitoses (arrow).

Figure 6

19-year-old man with primary synovial sarcoma of the lung. A, Immunoperoxidase stain for cytokeratin shows focal positivity in the tumor cells (KER, X200). B, Immunoperoxidase stain for bcl-2 protooncogene shows strong cytoplasmic positivity in the majority of the tumor cells (BCL-2, X200).