Synovial sarcoma arising from the pleura: a case report with ultrastructural and immunohistological studies.

Synovial sarcoma commonly occurs in the para-articular regions of the extremities, and rarely in the pleura. We report a 46-year-old woman with primary synovial sarcoma of the pleura. She was admitted with a complaint of left-sided chest pain and exertional dyspnea. She had previously undergone two operations for pleural neoplasm, at the ages of 33 and 36 years. A computed tomography scan revealed an expanded mass in the left thoracic cavity, involving the surrounding tissue. Macroscopic findings demonstrated a 25 x 25 x 15-cm grayish-white mass with hemorrhage beneath the pleura. Both epithelial and spindle cells were observed microscopically. Ultrastructural microscopy of the epithelioid cells demonstrated short, blunt microvilli on the luminal surface, and desmosomes between the neoplastic cells. Immunohistochemically, the tumor cells of the epithelial component were positive for embryonal membrane antigen (EMA), carcinoembryonic antigen (CEA), human mesothelial cells (HBME)-1, and cytokeratin, and the spindle cells were positive for vimentin. These findings led us to a diagnosis of primary synovial sarcoma of the pleura. She had no evidence of recurrence or metastasis after the third operation.