[Histopathology of gestational trophoblastic disease. An update].

The differential diagnosis of villous forms of gestational trophoblastic disease (GTD) includes hydropic abortion, complete and partial hytatidiform mole and placental mesenchymal dysplasia. In addition to histologic criteria, p57(KIP2) immunohistochemistry might be helpful. Choriocarcinoma represents the most immature form of GTD. This and downregulation of HSP-27 might contribute to the high chemosensitivity, compared to placental site (PSTT) and epitheloid trophoblastic tumor (ETT). Within the differential diagnosis of the non-villous forms of GTD an algorithmic approach of immunohistochemistry is very helpful. With an incidence of 1.6% of all abortions within the first trimester the exaggerated placental site reaction (EPS) is rare. There is no molecular indication that the EPS represents a precursor lesion of PSTT. The morphologic prediction of the behaviour of PSTT is not well established. Factors which might be associated with adverse outcome are age >35 years, interval since last pregnancy >2 years, growth outside the uterus, deep myometrial invasion, destructive growth, extensive coagulative necrosis, presence of cells with clear cytoplasm, high mitotic rate and a Ki-67 labeling index >50%. Recent molecular data suggest a neoplastic transformation of (cyto-) trophoblastic stem cells, within the pathogenesis of (non-villous) GTD. The detection of target molecules for a targeted therapy is currently irrelevant.