HLA expression by trophoblast of invasive moles

HLA expression by the trophoblast in invasive hydatidiform mole was analysed by immunoperoxidase staining. In the invading villi of an invasive mole, villous trophoblast, both syncytiotrophoblast and cytotrophoblast, failed to show a positive reaction for HLA-A, -B and -C and HLA-DR. By contrast, extravillous trophoblast showed an intense reaction for HLA-A, -B and -C. The distribution of HLA antigens in the invading villi was the same as in the non-invading villi, and the antigens were also indistinguishable from those noted in non-invasive hydatidiform moles. The histopathology of invasive mole may suggest that it is a malignant neoplasm. This immunohistochemical study, however, lends support to the current view that invasive mole is a variant of a benign hydatidiform mole rather than a form of malignant trophoblastic disease.