Human chorionic gonadotrophin and alpha-fetoprotein in testicular germ cell tumours: a retrospective immunohistochemical study.

A series of testicular germ cell tumours (46 seminomas and 27 non-seminomas) was studied immunohistochemically with regard to the presence of alpha FP and HCG. In three seminomas, HCG reactive syncitiotrophoblast-like giant cells (STLG) were found. Immunoreactive alpha FP did not occur in seminomas. In differentiated mature teratomas HCG or alpha FP could not be demonstrated. In embryonal carcinomas with or without teratoma (MTI/MTU/MTT) HCG immunoreactivity was found in 83%, usually localized in STLG. In 75% of these tumours alpha FP could be demonstrated. This protein was localized in foci of endodermal sinus or yolk sac differentiation, but also in single cells and cell clusters in areas of embryonal carcinoma. In some cases syncitial cells were present which contained both HCG and alpha FP. Immunostaining of tumour markers appeared not to provide important additional criteria for classification of these tumours in the currently available classifications. The significance of HCG containing STLG in seminomas deserves further investigation. Prospective studies of embryonal carcinoma with or without teratoma (MTI/MTU/MTT) will be necessary to evaluate the possible prognostic importance of the presence of alpha FP or HCG or both.