Localization OF HCGα and HCGβ in Trophoblastic Tumors

Tissue distribution of the subunits of human chorionic gonadotropin (hCG), hCGα and hCGβ, in eight cases of trophoblastic tumors, including four cases of choriocarcinoma, two cases of invasive mole and two cases of hydatidiform mole, was studied by the immunoperoxidase method. In villous trophoblasts of hydatidiform mole, though distribution patterns in the cytoplasm differed, both hCGα and hCGβ were revealed to be located chiefly in the syncytiotrophoblast and to a lesser extent in the cytotrophoblast suggesting that hCG is not only localized but also synthesized mainly in the syncytiotrophoblast while the immature cytotrophoblast does not produce hCG. In invasive mole, villi were markedly degenerative, composed mostly of the syncytiotrophoblast with scarce intraplasmic hCGα. This condition of the villi is considered to be the result of intensive chemotherapy prior to operation, and may be explained by the so-called cellular effect of transient increase of hCG in the serum during chemotherapy. In choriocarcinoma, strongly immunoreactive products of hCGα and hCGβ were observed in the syncytiotrophoblast-like cells with several nuclei scattered like islands in the invading front. These findings are considered to be related to the local immunosuppressive effect of hCG on invasion and survival of choriocarcinoma cells analogous to the syncytiotrophoblast in the trophoblastic shell and column of normal pregnancy.