Embryonal rhabdomyosarcoma arising in a mature teratoma of the testis: a case report.

We report a case of embryonal rhabdomyosarcoma present in the primary excision of an intratesticular purely mature teratoma. Testicular mature and immature teratomas are usually associated with other germ cell tumors. Nongerminal malignancies that tend to occur in gonadal and extragonadal teratomas are often epithelial. Sarcomas of all types are less frequent but embryonal rhabdomyosarcomas are encountered predominantly. This sarcomatous element can be present in the primary excision or it can appear after chemotherapy in the metastases. Usually, prognosis is dependent on the degree of aggressiveness of the sarcomatous component. A review of the literature reveals that it is unusual for an embryonal rhabdomyosarcoma to develop on purely mature teratoma. We report a case in the testicle. During followup metastases arise rapidly from the purely embryonal rhabdomyosarcomatous component. The accurate diagnosis of this unusual sarcomatous component is of paramount importance because of the implications for therapy.