Immunohistochemical demonstration of alpha-fetoprotein in testicular germ cell tumors.

Immunohistochemically AFP was demonstrated in testicular germ cell tumors using the PAP method after Sternberger. AFP immunoreactivity was found in the yolk sac components of combined germ cell tumors. But embryonal carcinomas showed positive immunoperoxidase reaction for AFP in the cytoplasm of single cells in the solid masses and in areas forming tubular patterns. Also embryoid bodies in a polyembryoma and in combined germ cell tumors showed an AFP reactivity. Furthermore in immature teratomas positive staining was seen in epithelial cells of primitive cysts, adenoid and gut-like structures of probably entodermal origin. The positively reacting structures of combined germ cell tumors could be interpreted as early stages of embryonal development. Thus the results support the theory of totipotency of cells of embryonal carcinoma.