Hydatidiform mole: A tumor that forms in the uterus as a mass of cysts resembling a bunch of grapes. Moles occur during the childbearing years. They do not spread outside of the uterus. However, a malignancy called choriocarcinoma may start from a hydatidiform mole.
In its early stages, a hydatidiform mole may look like a normal pregnancy. Diagnosis is based on a history of lack of fetal movement, a pelvic examination, an ultrasound, and blood test to look for high levels of a hormone called beta HCG (beta human chorionic gonadotropin). If a woman is not pregnant and HCG is in the blood, it can be a sign of an hydatidiform mole.
Treatment is removal of the mole by dilation and curettage (D & C) and suction evacuation or by surgery to remove the uterus (hysterectomy). After surgery, regular blood tests are done to make sure the level of beta HCG in the blood falls to normal levels. If the blood levels of beta HCG do not go down to normal or increase, more tests are needed to see whether the mole has persisted or there may be choriocarcinoma.
Hydatidiform moles arise in an extraordinary manner. They are the products of parthenogenesis: the development of a germ cell without equal contributions of DNA from both the egg and the sperm. All the chromosomes in hydatidiform moles come from the woman's male partner.
There are two types of gestational trophoblastic tumors: hydatidiform mole and choriocarcinoma. Hydatidiform mole is also known as a molar pregnancy.