Adenocarcinoma arising within a testicular metastasis

Teratoma with malignant transformation is defined as the emergence of a non-germ cell tumor from a teratoma. Although extremely rare in extraovarian sites, cases have been reported that involve primary extragonadal germ cell tumors with transformation to variants of sarcoma. We report a 54-year-old man who was found to have adenocarcinoma arising within a mature teratomatous retroperitoneal metastasis 15 years after treatment of a nonseminomatous testicular germ cell tumor. The tumor was successfully excised and he remains without evidence of disease.