Sarcoma arising in a residual testicular teratoma after cytoreductive chemotherapy.

A case of testicular teratoma metastasized to the retroperitoneum and after cytoreductive chemotherapy was noted to contain areas of frank sarcoma. Sarcomatous areas included embryonal rhabdomyosarcoma with a pattern of sarcoma botyroides, alveolar rhabdomyosarcoma, and fibrosarcoma. These areas differed markedly from areas of immature teratoma, which composed the remainder of the retroperitoneal lesion and which also characterized the primary tumor. These sarcomatous areas were characterized by numerous mitoses, marked cellular pleomorphism and diagnostic histologic, ultrastructural, and immunocytochemical features. Residual germ cell tumors following cytoreductive chemotherapy are traditionally categorized as teratoma only or teratoma with embryonal carcinoma or choriocarcinoma for therapeutic and prognostic reasons. This case does not conform to this simple categorization and raises serious questions concerning subsequent therapeutic decisions.