Source:http://linkedlifedata.com/resource/umls/id/C0349557
NCI: A rare, highly malignant, epithelial tumor that develops from a hydatidiform mole (50%), following abortion (25%), or during normal pregnancy (22%). Histologically, choriocarcinomas consist of invasive and anaplastic trophoblastic tissue composed of cytotrophoblastic and syncytiotrophoblastic cells, secretion of human chorionic gonadotropin, and abundant vascularity. Because of rapid growth and a high propensity for hemorrhage, this neoplasm often constitutes a medical emergency. --2004