A man in his 40’s was found to have a right atrial mass, bilateral pulmonary nodules, and pleural effusion. Pleural fluid cytology revealed clusters showing papillary or glandular structure resembling adenocarcinoma, composed of columnar to short-spindle cells. CT-guided needle lung biopsy showed dense proliferation of spindle to oval cells with acinar and glandular structures. The tumor cells were positive for CAM5.2, vimentin, and bcl-2 in immunocytochemistry and immunohistochemistry. RT-PCR detected SYT-SSX1 fusion transcripts in paraffin-embedded tissue. No primary lesions were found except for the cardiac tumor, and a diagnosis of primary cardiac synovial sarcoma was made. The epithelioid clusters in the pleural effusion are a very interesting cytologic feature of synovial sarcomas.
