Adenocarcinoma arising from a mature cystic teratoma of the testis.

A 52-year-old male diagnosed pathologically with metastatic adenocarcinoma of the skin was referred to our department. Physical examination revealed a right scrotal mass the size of child's head and several skin tumors. Right high orchiectomy and resection of skin tumors were performed. Histopathological examination revealed a well-differentiated, mucinous adenocarcinoma originating from the gastrointestinal epithelium in a mature cystic teratoma (dermoid cyst) of the testis and metastatic mucinous adenocarcinoma of the skin. We made a diagnosis of teratoma with malignant transformation (TMT) of the testis. Combination chemotherapy with low-dose cisplatin/5'-deoxy-5-fluorouridine (CDDP/5'-DFUR) was initiated, but the patient died 8 months after orchiectomy. At autopsy, similar mucinous adenocarcinoma of the testis and the skin were observed at the metastatic sites.