New Diagnostic and Therapeutic Approaches to Gestational Trophoblastic Tumours

Gestational trophoblastic tumours (GTT) are unique in cancer biology since genetically they are either partially or completely paternally derived. GTT may occur after any form of pregnancy, but the most common presentation is with a hydatidiform mole (HM). The classical hydatidiform mole (CHM) is an androgenetic conceptus where the maternal genes have been deleted and the abnormal pregnancy presents between 8 and 12 weeks into gestation with vaginal bleeding and florid hydropic villi of trophoblast in the uterus and myometrium. Partial hydatidiform mole (PHM) is a triploid conceptus and again presents with vaginal bleeding, but with much less florid hydropic change in the trophoblastic villi; it commonly has some evidence of foetal development pathologically. Choriocarcinoma is a frank malignancy of the trophoblast and is an extremely vascular tumour, rapidly metastasising through the venous system to the lungs, brain and other sites. The incidence of malignancy following CHM is approximately 8% in the Charing Cross series and 0.5% after PHM. Choriocarcinoma can occur after molar pregnancies, full-term pregnancies and abortions. Over the last decade, a rare variant of choriocarcinoma, placental site trophoblastic tumour (PSTT), has been recognised pathologically and clinically. This tends to be a less widely metastasising tumour than choriocarcinoma and infiltrates locally in the pelvis.