GESTATIONAL TROPHOBLASTIC DISEASE (GTG38 ) SEP 2020 Definition Gestational trophoblastic disease (GTD) comprises a group of disorders spanning the premalignant conditions of complete and partial molar pregnancies (also known as hydatidiform moles) through to the malignant conditions of invasive mole, choriocarcinoma and the very rare placental site trophoblastic tumour (PSTT) and epithelioid trophoblastic tumour (ETT). The malignant potential of atypical placental site nodules (PSNs) remains unclear. If there is any evidence of persistence of GTD after primary treatment, most commonly defined as a persistent elevation of human chorionic gonadotrophin (hCG), the condition is referred to as gestational trophoblastic neoplasia (GTN). The diagnosis of GTN does not require histological confirmation. The diagnosis of complete mole, partial mole, atypical PSN and PSTT/ETT does require histological confirmation. How do molar pregnancies present to the clinicia...