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a malignant neoplastic disease of the uterus derived from chorionic epithelium, characterized by the production of high levels of human chorionic gonadotropin (HCG). The tumor may be an invasive hydatid mole (chorioadenoma destruens) formed by grossly enlarged vesicular chorionic villi or a malignant uterine choriocarcinoma that arises from nonvillous chorionic epithelium. One half of the cases of choriocarcinoma follow a molar pregnancy, 25% an abortion, 22.5% a normal pregnancy, and 2.5% an ectopic pregnancy. A hydatid mole invades the myometrium and often forms extrauterine nodules that may spread to distant sites. Choriocarcinoma forms a dark red hemorrhagic nodular tumor on or in the uterine wall and metastasizes early in its course to the lungs, brain, liver, bones, vagina, or vulva. Initial symptoms are vaginal bleeding and a profuse, foul-smelling discharge; a persistent cough or hemoptysis signals pulmonary involvement. As the disease progresses, there may be frequent hemorrhage, weakness, and emaciation. Diagnostic measures include serial assays to determine whether the HCG level in the blood is elevated and histological examination of specimens obtained by curettage. Hysterectomy is indicated in most cases, but surgery does not eliminate the possibility of a recurrence. Chemotherapy is effective in curing a large percentage of patients with trophoblastic tumors. Also called trophoblastic disease. See also choriocarcinoma, hydatid mole.