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Hydatidiform Mole

(Gestational Trophoblastic Disease; Molar Pregnancy)

By Pedro T. Ramirez, MD, Professor, Department of Gynecologic Oncology and Reproductive Medicine, David M. Gershenson Distinguished Professor in Ovarian Cancer Research, and Director of Minimally Invasive Surgical Research and Education, The University of Texas MD Anderson Cancer Center ; Gloria Salvo, MD, Rotating Research Resident, Department of Gynecologic Oncology and Reproductive Medicine, MD Anderson Cancer Center

A hydatidiform mole is growth of an abnormal fertilized egg or an overgrowth of tissue from the placenta.

  • Women appear to be pregnant, but the uterus enlarges much more rapidly than in a normal pregnancy.

  • Most women have severe nausea and vomiting, vaginal bleeding, and very high blood pressure.

  • Ultrasonography, blood tests to measure human chorionic gonadotropin (which is produced early during pregnancy), and a biopsy are done.

  • Moles are removed using dilation and curettage (D and C) with suction.

  • If the disorder persists, chemotherapy is needed.

Most often, a hydatidiform mole is an abnormal fertilized egg that 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, a full-term pregnancy, or a mislocated pregnancy (ectopic pregnancy). Rarely, a hydatidiform mole develops when there is a living fetus. In such cases, the fetus typically dies, and a miscarriage often occurs.

Hydatidiform moles are most common among women under 17 or over 35. In the United States, they occur in about 1 in 2,000 pregnancies in the United States. For unknown reasons, hydatidiform moles are almost 10 times more common in Asian countries.

Hydatidiform moles are a type of gestational trophoblastic disease.

Did You Know...

  • An abnormal fertilized egg or abnormal placental tissue can overgrow, causing symptoms similar to those of pregnancy, but the abdomen becomes larger more rapidly.

Types of gestational trophoblastic disease

Gestational trophoblastic disease is a group of disorders that develop from cells (called trophoblasts) that surround a developing embryo and that eventually form the placenta and amniotic sac. The affected cells grow abnormally and multiply quickly.

There are two main forms of gestational trophoblastic disease:

  • Hydatidiform moles (also called molar pregnancy), which are usually not cancerous

  • Gestational trophoblastic neoplasia, which is usually cancerous

Gestational trophoblastic neoplasia includes the following subtypes:

  • Invasive moles (called chorioadenoma destruens)

  • Choriocarcinomas

  • Placental-site trophoblastic tumors

  • Epithelioid trophoblastic tumors

About 80% of hydatidiform moles are not cancerous. The rest tend to persist and invade surrounding tissue. Most of these moles are invasive moles. About 2 to 3% of hydatidiform moles develop into choriocarcinomas. Choriocarcinomas can spread quickly through the lymphatic vessels or bloodstream.

Placental-site trophoblastic tumors and epithelioid trophoblastic tumors are very rare.

Symptoms

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. As parts of the mole deteriorate, small amounts of tissue, which resemble a bunch of grapes, may pass through the vagina. These symptoms indicate the need for prompt evaluation by a doctor.

Hydatidiform moles can cause serious complications, including the following:

If choriocarcinoma develops, women may have other symptoms, caused by spread (metastasis) to other parts of the body.

Diagnosis

  • Blood tests

  • Ultrasonography

  • Biopsy

Often, doctors can diagnose a hydatidiform mole shortly after it forms. They suspect a hydatidiform mole based on symptoms, such as a uterus that is much larger than expected and a vaginal discharge of grapelike tissue.

A pregnancy test is done. If women have a hydatidiform mole, results are positive, but no fetal movement and no fetal heartbeat are detected.

Blood tests to measure the level of human chorionic gonadotropin (hCG—a hormone normally produced early in pregnancy) are done. If a hydatidiform mole or another type of gestational trophoblastic disease is present, the level is usually very high because these tumors produce a large amount of this hormone.

Ultrasonography is done 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).

A sample of tissue is removed during D and C or obtained when tissue is passed and is then examined under a microscope (biopsy) to confirm the diagnosis.

If gestational trophoblastic disease is diagnosed, tests are done to find out if the tumor has spread from where it started to other parts of the body (staging).

Prognosis

With treatment, many women are cured. The likelihood of cure depends on whether the mole has spread and other factors:

  • If the mole has not spread: Virtually 100%

  • If the mole has spread but is considered low risk: 90 to 95%

  • If the choriocarcinoma has spread widely and is considered high risk: 60 to 80%

Most women who have had a hydatidiform mole can have children afterward and do not have a higher risk of a miscarriage, complications during pregnancy, or children with birth defects.

About 1% of women who have had a hydatidiform mole have another one. So if women have had a hydatidiform mole, ultrasonography is done early in subsequent pregnancies.

Treatment

  • Removal of the mole

  • Tests to check for recurrence and/or spread

  • If needed, chemotherapy

A hydatidiform mole or any type of gestational trophoblastic neoplasia is completely removed, usually by dilation and curettage (D and C) with suction. Only rarely is removal of the uterus (hysterectomy) necessary.

Tests to determine whether women need additional treatment are done after the mole is removed.

A chest x-ray is taken to see whether the mole has spread to the lungs.

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 10 weeks, and remains normal, and no further treatment is needed. If the level does not return to normal, the disease is considered persistent. Then, computed tomography (CT) of the brain, chest, abdomen, and pelvis is done to determine whether choriocarcinoma has developed and spread.

Chemotherapy is needed if the mole persists or has spread but is considered low risk. Chemotherapy may consist of only one drug (methotrexate or dactinomycin). If this treatment is ineffective, a combination of chemotherapy drugs (such as etoposide, methotrexate, actinomycin-D, cyclophosphamide, and vincristine) may be used, or hysterectomy may be done.

If the mole has spread widely and is considered high risk, several chemotherapy drugs are used.

Women who have had a hydatidiform mole removed are advised not to become pregnant for 6 months. Oral contraceptives are frequently recommended, but other effective contraceptive methods can be used. Pregnancy is delayed so that doctors can make sure that treatment was successful.

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