Gestational trophoblastic disease: histopathological diagnosis in the molecular era

Gestational trophoblastic disease is a heterogeneous group of proliferative disorders of the placental trophoblasts, often with challenging morphology, posing diagnostic problems for the general, even specialty pathologists. In this review we discuss characteristic histological features of complete- and partial hydatidiform moles, with special focus on the diagnosis of hydatidiform moles evacuated at early stage and their mimics. The diagnostic criteria and potential pitfalls in the diagnosis of gestational choriocarcinoma and two rare, unique neoplasms of the intermediate trophoblast – placental site trophoblastic tumour and epithelioid trophoblastic tumour – are presented, along with their differential diagnoses from two tumour-like conditions including exaggerated placental site and placental site nodule. We also review the current practice of immunohistochemistry, ploidy analysis and molecular genotyping in the diagnosis of gestational trophoblastic disease. Finally, how molecular testing may change the future diagnostic algorithm of gestational trophoblastic diseases is discussed.