A 25-yrs-old woman in her 15 week of pregnancy presents with uterine bleeding and passage of a small amount of watery fluid and tissue. She is found to have a uterus that is much larger than estimated by her gestational dates. Her uterus is found to be filled with cystic, avascular, grapelike structures that do not penetrate that uterine wall. No fetal pas are fo Most likely diagnosis?

* Gestational trophoblastic diseases include benign hydatidiform mole (paial and complete), invasive mole (chorioadenoma destruens), placental site trophoblastic tumor, and choriocarcinoma. * Hydatidiform moles are composed of avascular, grapelike structures that do not invade the myometrium. In complete (classic) moles, all the chorionic villi are abnormal and fetal pas are not found. * They have a 46,XX diploid pattern and arise from the paternal chromosomes of a single sperm by a process called androgenesis. * In paial moles, only some of the villi are abnormal and fetal pas may be seen. These moles have a triploid or a tetraploid karyotype and arise from the feilization of a single egg by two sperm. * About 2% of complete moles may develop into choriocarcinoma, but paial moles are rarely followed by malignancy Invasive moles penetrate the myometrium and may even embollze to distant sites. * A similar lesion is the placental site trophoblastic tumor, which is characterized by invasion of the myometrium by intermediate trophoblasts. * Gestational choriocarcinomas, composed of malignant proliferations of both cytotrophoblast and syncytiotrophoblasts without the formation of villi, can arise from either normal or abnormal pregnancies: 50% arise in hydatidiform moles, 25% in cases of previous aboion, 22% in normal pregnancies, and the rest in ectopic pregnancies or teratomas. * Both hydatidiform moles and choriocarcinomas have high levels of human chorionic gonadotropin (hCG); the levels are extremely high in choriocarcinoma unless considerable tumor necrosis is present.