Abstract
Background : Most synovial sarcomas arise around joints, and primary synovial sarcoma of the lung is rare. We report a case of primary synovial sarcoma of the right lung.
Case : A 48-year-old man was admitted to our hospital because of an abnormal shadow in the right middle lung field detected during a medical checkup. A CT examination revealed a round mass in the hilum of the right lung. Right upper and middle lobectomy was performed, and touch smear cytology of the tumor showed fascicles of spindle-shaped to round tumor cells containing bland, uniform nuclei, and finely light-green-staining cytoplasm. Histologically, the tumor was composed of densely proliferating uniform spindle-shaped to oval cells in fascicles. The tumor cells were immunohistochemically positive for vimentin, CD99, bcl-2, cytokeratin AE1/AE3, and EMA. RT-PCR performed on paraffin-embedded sections demonstrated fusion gene transcripts of SYT-SSX1. A diagnosis of synovial sarcoma of the lung, monophasic fibrous type, was made.
Conclusion : Synovial sarcoma of the lung is rare. Diagnosis of spindle-cell tumors by cytological examination alone is difficult. To achieve a definitive diagnosis, it is important to include synovial sarcoma in the differential diagnosis during the cytodiagnostic procedure, and immunohistochemistry, cytogenetic, and molecular studies are necessary.
