Alpha-fetoprotein (AFP) and human chorionic gonadotropin (HCG) in testicular germ cell tumours. A prospective immunohistochemical study.

189 orchidectomy specimens with germ cell tumours (95 pure seminomas and 94 non-seminomas) were studied for the presence of alpha-fetoprotein (AFP) and human chorionic gonadotropin (HCG) with the indirect immunoperoxidase technique. All seminomas were AFP negative, while 66% of the non-seminomas were positively stained for AFP. 21% of pure embryonal carcinomas (EC), 25% of EC components in mixed tumours, all yolk sac tumour (YST) components, 20% of pure teratomas (T) and 47% of T components were AFP positive. In EC and YST the immunohistochemical staining depicted characteristic previously unrecognized histological structures, presumably representing patterns of further differentiation. HCG was demonstrated in all choriocarcinoma (CC) components in the syncytiotrophoblasts and in syncytiotrophoblast-like cells (STLC) in 8% of seminomas and 30% of non-seminomas. 70% of all non-seminomatous tumours were positively stained for AFP and/or HCG. Neither AFP nor HCG positivity of the tumour tissue was especially associated with metastatic disease. Carcinoma-in-situ (CIS) present in seminiferous tubules adjacent to the tumours was never positively stained for AFP, but for HCG in a few cases.