Neuroendocrine Tumor as a Somatic-Type Malignancy in Metastatic Teratoma.

Testicular germ cell tumors represent less than 1% of all cancer diagnoses in men. Postpubertal-type teratomas are a form of nonseminomatous germ cell tumor derived from 2 or more embryonic germ cell layers. Rarely, these tumors have been shown to develop somatic-type malignancy, where a nongerm cell malignancy such as carcinoma or sarcoma arises in a germ cell tumor. Neuroendocrine tumors as a somatic-type malignancy in teratomas are extremely rare. Here, we report a high-grade neuroendocrine tumor arising within a metastatic teratoma in a 25-year-old man.