Women often learn they’re pregnant when they take a pregnancy test that checks for levels of human chorionic gonadotropin (hCG), the so-called pregnancy hormone, in their urine or blood. In very rare cases, however, a woman who believes she is pregnant may actually have gestational trophoblastic disease, an uncommon condition which may occur when someone is trying to get pregnant, which raises a woman’s hCG levels. Some women with gestational trophoblastic disease may develop gestational trophoblastic tumors, a rare type of cancer that only occurs in women who have been pregnant.
Gestational trophoblastic tumors are more common among older and younger women (those over 35 and under 17) and women who have previously had gestational trophoblastic disease, including molar pregnancies.
Doctors are able to treat gestational trophoblastic tumors, and in most cases, women are able to become pregnant after they recover.
What are gestational trophoblastic tumors?
Gestational trophoblastic tumors are rare cancers that develop in the uterus after a woman has become pregnant. It’s also known as gestational trophoblastic neoplasia. With this condition, cells that should have developed into a placenta to support a fetus instead form cancerous tumors.
In a healthy pregnancy, after the sperm and egg combine, the cells multiply and form an embryo, which soon develops into a fetus. Specialized cells called trophoblasts develop and become part of the placenta, which attaches to the uterus wall and helps to provide nourishment from the mother to the growing fetus.
When someone develops gestational trophoblastic disease, the trophoblasts develop into cysts or tumors, instead of helping to form the placenta. In many cases, this happens when a molar pregnancy occurs. During a molar pregnancy:
- One or two sperm cells fertilize an abnormal egg that’s missing the mother’s genetic material—it only contains the father’s DNA. When this happens, fetal tissue doesn’t develop.
- Two sperm cells fertilize a single egg cell that contains the mother’s genetic material. When this happens, fetal tissue may develop, but it will contain too much genetic material (two sets of genes from the father and one from the mother), and the pregnancy ends in miscarriage.
A molar pregnancy may lead to the growth of cysts or non-cancerous tumors.
Gestational trophoblastic tumors may develop when tissue is left behind in the uterus after a molar pregnancy, a miscarriage, an abortion, or even a healthy pregnancy. The tumors may cause the uterus to swell in size, even though a fetus is not present.
About 1 in 1,000 pregnancies result in gestational trophoblastic disease, such as a molar pregnancy, but gestational trophoblastic tumors are much less common, with only about 1 in 40,000 pregnancies affected.
There are four types of gestational trophoblastic tumors, from most common to rare:
- Invasive moles, which remain within the uterus
- Choriocarcinomas, which may spread to other parts of the body, including the brain and lungs
- Placental-site trophoblastic tumors, a rare, slow-growing cancer that develops at the spot where the placenta attaches to the uterine wall, and which may spread to other body parts, such as the lymph nodes or lungs
- Epithelioid trophoblastic tumors, which are extremely rare and which may spread to the lungs
What causes gestational trophoblastic tumors?
Doctors don’t yet know why some pregnant women develop gestational trophoblastic tumors, but they’re more common among women who have had molar pregnancies and those who are age 35 or older.
What are the symptoms of gestational trophoblastic tumors?
Women who have gestational trophoblastic tumors may experience:
- Abnormal vaginal bleeding
- Missed menstrual periods
- Pelvic pain
- A larger-than-expected uterus during pregnancy, which may result in a larger-than-expected abdomen earlier in pregnancy
- Higher-than-expected levels of hCG, the pregnancy hormone
- Post-pregnancy bleeding that persists for longer than 6 to 8 weeks
What are the risk factors for gestational trophoblastic tumors?
Women are more likely to develop gestational trophoblastic tumors if they:
- Have had a previous molar pregnancy or another form of gestational trophoblastic disease
- Have had other unsuccessful pregnancies, such as miscarriage, ectopic pregnancy, or abortion
- Have hyperthyroidism, an overactive thyroid
- Become pregnant after age 35 or before age 17
- Smoke cigarettes
How are gestational trophoblastic tumors diagnosed?
Doctors will obtain a medical history, perform a physical exam, and order a variety of tests to diagnose gestational trophoblastic tumors.
A doctor will first ask about symptoms—if the woman has experienced vaginal bleeding and/or pelvic pain. The doctor will also ask about pregnancy history, and whether she has experienced any miscarriages, ectopic pregnancies, molar pregnancies, abortions, or live births.
During a pelvic exam, the doctor will check for any abnormalities, including a uterus that measures larger than it should during that stage of pregnancy.
The doctor should order a urine test to see if a woman’s hCG hormone levels are high.
Blood tests can also look at hCG levels, as well as thyroid function and anemia, which may suggest gestational trophoblastic disease.
When gestational trophoblastic tumors are suspected, doctors may diagnose the condition when someone has abnormal, high hCG readings over a period of weeks.
Doctors don’t perform a biopsy to diagnose gestational trophoblastic tumors, because certain types (choriocarcinomas) may bleed heavily when biopsied. Instead, they perform suction curettage and test the tissue that they remove.
After doctors diagnose gestational trophoblastic tumors, they use imaging tests such as ultrasound, CT scan, MRI or chest X-ray to determine whether the cancer has spread. They may also order a lumbar puncture, sampling some spinal fluid from the lower back, to see if the cancer has spread to the brain or spinal cord.
How are gestational trophoblastic tumors treated?
To remove gestational trophoblastic tumors, doctors may perform the following procedures:
- Suction curettage, which uses a vacuum device to remove tumors and other tissue from the uterus through the dilated cervix. The inner walls of the uterus are then gently scraped, to ensure that all cancerous tissue has been removed.
- Hysterectomy, which removes the tumors, along with the entire uterus, with or without the Fallopian tubes, ovaries and/or cervix. Because a woman can no longer become pregnant once this is done, some women opt not to elect this option when they’re presented with a choice. (For placental-site trophoblastic tumors and epithelioid trophoblastic tumors, hysterectomy is the standard of care, as those cancers don’t respond to chemotherapy.) Doctors may also remove neighboring lymph nodes to see if the cancer has spread.
After surgery, doctors may offer additional treatments to ensure that all of the cancer cells have been eradicated, and to lower the risk that the cancer will return. Options include:
- Chemotherapy, a medication that can kill cancer cells. For lower-risk tumors, doctors may prescribe a single chemotherapy drug. For higher-risk tumors that may spread to other body parts, doctors may provide combination therapy, offering two or more chemotherapy drugs simultaneously. Doctors will monitor a woman’s hCG levels throughout chemotherapy treatment to see if the levels drop, which is a sign that treatments have been effective.
- Radiation therapy, which may be offered in combination with chemotherapy when cancer has spread to other body parts, including the brain or the lungs. It may be administered externally or internally, depending on the diagnosis.
What is the outlook for people with gestational trophoblastic tumors?
About 99 percent of women who are diagnosed with gestational trophoblastic tumors fully recover, and the condition shouldn’t impair a woman’s fertility.