Primitive neuroectodermal tumor arising in a testicular teratoma with retroperitoneal metastasis: report of an interesting case with review of literature.

Teratomas with malignant transformation occur in approximately 3 to 6% of patients with metastatic germ cell tumors treated with platinum-based chemotherapy. The histology of the nongerm cell (somatic) malignant elements most commonly includes carcinoma and various types of sarcomas; however, so far as the primitive neuroectodermal tumors (PNETs) are concerned the experience is quite limited. There are only seven documented case reports and occasional series of PNET in association with testicular teratoma either in the primary site or in the metastatic location. We report a relatively unusual case of PNET arising in a malignant mixed germ cell tumor in a 35-year-old man.