Malignant transformation of testicular teratoma to primitive neuroectodermal tumor.

Teratoma is a common germ cell tumor that affects young adult males. A small number of testicular teratomas have the potential for malignant transformation along endodermal, ectodermal, or mesodermal lines. The metastatic mixed germ cell tumor we reported consists of the primitive neuroectodermal tumor (PNET) with mature teratoma.