Histopathological diagnosis of hydatidiform mole: contemporary features and clinical implications.

Gestational trophoblastic neoplasia (GTN) encompasses several entities including complete (CHM) and partial (PHM) hydatidiform mole (HM), malignant choriocarcinoma, and placental-site trophoblastic tumor. HMs are genetically abnormal, nonviable conceptions, which are associated with significantly increased risk for development of complications due to persistence of abnormal trophoblast (persistent GTN; pGTN), which occurs following 15% of CHM and 0.5% of PHM. Diagnostic histological features of HM are present in the first trimester but these features differ from those traditionally described in the later second trimester. The characteristic morphological findings of early HM include aspects of villous dysmorphism and abnormal villous trophoblast hyperplasia, with other specific features allowing reliable distinction between CHM and PHM. Optimal management of molar disease depends on its early histological identification and subsequent surveillance by measurement of maternal human chorionic gonoadotropin (hCG) for detection of pGTN based on rising or plateuing hCG levels such that early effective treatment is possible.