Immunohistochemistry of molar and non-molar placentas with special reference to their differential diagnosis.

An immunohistochemical study analyzing distributions of β‐subunit human chorionic gonadotropin (βHCG), human placental lactogen (HPL), placental alkaline phosphatase (PLAP), and monoclonal anti‐cytokeratin (PKK1) was undertaken to determine whether the reactivity of these antigens might assist in the differential diagnosis of molar and non‐molar hydropic placentas. A total of 16 complete hydatidiform moles, 15 partial hydatidiform moles, 12 hydropic abortuses and 39 non‐hydropic placentas with gestational age ranging from 4 to 40 weeks was examined. In both the complete and partial moles, many syncytiotrophoblasts stained for βHCG, HPL, PLAP and PKK1 although the staining intensity of βHCG in the partial moles was weak compared with the complete moles. The staining patterns in the hydropic abortuses were almost the same as those in the normal first trimester placentas and had no distinct features from the partial moles. Trophoblastic hyperplasia is an essential feature in differentiating partial moles from hydropic abortuses. With regard to the immunostaining patterns of these antibodies, there was no significant difference to enable delineation between partial and complete moles, or between a hydropic abortus and a partial mole. Monoclonal anti‐cytokeratin was most sensitive for trophoblasts, but less specific for intermediate trophoblasts than HPL. Although an immunohistochemical study using antibodies against βHCG, HPL, PLAP and PKK1 is very useful for characterizing various trophoblasts, it is considered that an immunohistochemical study may not be a suitable tool for the differential diagnosis of molar and non‐molar hydropic placentas.