An ultrastructural, immunohistochemical, and cytogenetical study of a monophasic pulmonary synovial sarcoma: implications of the frequent ultrastructure of oligocilia and concentric membranous bodies with positive immunostaining for VS38c and MEF2.

A rare case of a monophasic pulmonary synovial sarcoma is reported. A 44-year-old Japanese man underwent lower lobectomy for a nodular mass in his right lung. Immunohistochemical study of the excised primitive spindle cell sarcoma revealed occasional positive stains by hitherto reported antigens of S-100, cytokeratin 7, high molecular weight cytokeratin (34 beta E12), pankeratin (AE1/AE3), and EMA, which were helpful for the differential diagnosis of other spindle cell sarcomas. Furthermore, positive immunostains for MEF2, VS38c (plasma cell antigen), and bcl-2 were rather significant findings in the present case. The definitive evidence that molecular genetic analysis showed a clonal single electrophoretic band of SYT-SSX mutated chimera gene was conclusive for the pathological diagnosis. The implications of the frequently seen ultrastructure of oligocilia and concentric membranous bodies with positive stains for VS38c and MEF2 are discussed. In the difficult pathological diagnosis of a rare and undifferentiated type of sarcoma with unusual clinicopathological features generated at an unusual site, comprehensive ultrastructural, immunohistochemical, and cytogenetic studies will lead to the correct pathological diagnosis and elucidate the detailed characteristics of the tumor.