Using an immunoperoxidase technique, a series of 13 extragonadal germ cell tumors were screened for the presence of 7 different antigens: human chorionic gonadotropin, beta-subunit (beta-hCG), pregnancy-specific beta 1-glycoprotein (SP1), human placental lactogen (hPL), carcinoembryonic antigen (CEA), alpha-fetoprotein (AFP), alpha 1-antitrypsin (alpha-AT) and ferritin. Syncytial giant cells in embryonal carcinoma and choriocarcinoma were positive for beta-hCG and SP1, while isolated foci of mononuclear cells in the embryonal carcinoma stained for AFP, alpha-AT and ferritin. Yolk sac tumor components showed immunoreactivity for AFP, alpha-AT and ferritin. In seminomas, a positive reaction for ferritin was found only in isolated cells of 2 cases. One seminoma was positive for alpha-AT. Teratomas were negative for all antigens, except for CEA and SP1 in duct-lining cells of sweat glands in one teratoma. Germ cell tumors of extragonadal sites appear to exhibit the same antigenic markers as their gonadal counterparts. Such similarities lend support to the hypothesis of a common cell origin of these neoplasms
