Hydatidiform Mole

A hydatidiform mole is growth of an abnormal fertilized egg or an overgrowth of tissue from the placenta. Most often, a hydatidiform mole is an abnormal fertilized egg. The abnormal egg develops into a hydatidiform mole rather than a fetus (a condition called molar pregnancy). However, a hydatidiform mole can develop from cells that remain in the uterus after a miscarriage or a full-term pregnancy. Rarely, a hydatidiform mole develops when the fetus is normal. About 80% of hydatidiform moles are not cancerous and disappear spontaneously. About 15 to 20% invade the surrounding tissue and tend to persist. Of these invasive moles, 2 to 3% become cancerous and spread throughout the body; they are then called choriocarcinomas. Choriocarcinomas can spread quickly through the lymphatic vessels or bloodstream. The risk of hydatidiform moles is highest for women who become pregnant before age 17 or in their late 30s or later. Hydatidiform moles occur in about 1 of 2,000 pregnancies, and for unknown reasons, are nearly 10 times more common among Asian women.

Symptoms & Diagnosis
Women who have a hydatidiform mole feel as if they are pregnant. But because hydatidiform moles grow much faster than a fetus, the abdomen becomes larger much faster than it does in a normal pregnancy. Severe nausea and vomiting are common, and vaginal bleeding may occur. These symptoms indicate the need for prompt evaluation by a family doctor. Hydatidiform moles can cause serious complications, including infections, bleeding, and preeclampsia or eclampsia.
Often, doctors can diagnose a hydatidiform mole shortly after conception. No fetal movement and no fetal heartbeat are detected. As parts of the mole decay, small amounts of tissue that resemble a bunch of grapes may pass through the vagina. After examining this tissue under a microscope, a pathologist can confirm the diagnosis.
Ultrasonography may be performed to be sure that the growth is a hydatidiform mole and not a fetus or amniotic sac (which contains the fetus and fluid around it). Blood tests to measure the level of human chorionic gonadotropin (HCG-a hormone normally produced early in pregnancy) may be performed. If a hydatidiform mole is present, the level is usually very high because the mole produces a large amount of this hormone.

Treatment
The cure rate for a hydatidiform mole is virtually 100% if the mole has not spread. The cure rate is 60 to 80% if the hydatidiform mole has spread widely. Most women can have children afterwards and do not have a higher risk of having complications, a miscarriage, or children with birth defects. About 1% of women who have had a hydatidiform mole have another one. So for women who have had a hydatidiform mole, ultrasonography is performed early during subsequent pregnancies. A hydatidiform mole that does not disappear spontaneously is completely removed usually by dilation and curettage (D and C) with suction. Only rarely is removal of the uterus (hysterectomy) necessary. If the hydatidiform mole is detected, a chest x-ray is performed after surgery to make sure that it has not become cancerous (that is, a choriocarcinoma) and spread to the lungs. After surgery, the level of human chorionic gonadotropin in the blood is measured to determine whether the hydatidiform mole was completely removed. When removal is complete, the level returns to normal, usually within 8 weeks, and remains normal. Women who have had a mole removed are advised not to become pregnant for 1 year. Hydatidiform moles do not require chemotherapy, but choriocarcinomas do. Usually, only one drug (methotrexate or dactinomycin) is needed. Sometimes both or another combination of chemotherapy drugs is needed.
[Merck]