Cellular localization of AFP, hCG and its free subunits, and SP1 in embryonal carcinoma of the testis and ovary.

An immunohistological study of AFP, hCG and its free subunits, and SP1 was investigated in 10 cases of non-seminomatous germ cell tumors of the testis and ovary. AFP was demonstrated in mononuclear embryonal tumor cells within embryonal carcinoma in a narrow sense, frequently in association with yolk sac tumor. AFP was more consistently demonstrated in vacuolated or elongated cells of yolk sac tumor, in which continuous transformation from tubular patterns of embryonal carcinoma was shown with positive reactions for AFP. The hCG was demonstrated in syncytiotrophoblastic giant cells scattered among the embryonal carcinoma, but rarely in mononuclear large cells. The occurrence of hCG and beta subunit was more frequently observed than a subunit or SP1, suggesting the unbalanced synthesis of hCG and free subunit in choriocarcinomatous element associated with embryonal carcinoma. These findings support the view that embryonal carcinoma has a developmental potential to the extra-embryonic components of both choriocarcinoma and yolk sac tumor.