Pathology of trophoblast.

In summary, recent light microscopic studies, complemented by immunocytochemical and cytogenetic techniques, have demonstrated profound differences in the etiology, morphology, and clinical behavior of various forms of GTD. In addition, in vitro studies combined with immunohistochemical and ultrastructural analysis of normal trophoblast have provided new insight into the factors that coordinate the interactions of trophoblastic and maternal cells at the implantation site and have elucidated some of the mechanisms that regulate normal trophoblastic invasion. Analysis of the studies of normal and neoplastic trophoblast suggests that each of the specific forms of GTD is related to discrete pathologic aberrations occurring at different stages of gametogenesis and placentation. The results of these studies are examined in light of what is known about the pathobiology of GTD and are correlated with the histologic classification of GTD developed by the International Society of Gynecological Pathologists under the auspices of the World Health Organization.