Serum protein distribution in hydatidiform mole. An immunohistochemical study.

In normal placentas during the first trimester of pregnancy, the syncytiotrophoblast appeared to be immunoreactive to alpha-antitrypsin (alpha 1-AT), alpha 1-antichymotrypsin, albumin, IgG, and transferrin. The underlying cytotrophoblast was negative for these same serum proteins. In the hydatidiform mole, these findings were profoundly different. The syncytiotrophoblast lost its immunoreactivity to albumin, IgG, transferrin, and, less frequently, to alpha 1-AT. Furthermore, the underlying cytotrophoblast became immunoreactive to albumin, alpha 1-AT, IgG, transferrin, ferritin, orosomucoid, and, sometimes, to alpha 1-antichymotrypsin. This altered immunohistochemical pattern suggested a notable change in the pinocytotic activity of the trophoblast in the placenta during molar degeneration. The absence of pinocytosis in the syncytiotrophoblast for several proteins can be explained by the partial loss of specific membrane receptors. The contemporaneous appearance of numerous serum proteins in the cytotrophoblast could indicate an activation, not only proliferative, but also functional, in the germinative cytotrophoblast. Diagnostically, this histochemical finding in the hydatidiform mole, which was quite different from that seen in normal placentas during the first trimester of pregnancy, could provide additional evidence concerning trophoblastic abnormalities in the chorionic villi during molar degeneration.