What are the types of GTD?
Gestational trophoblastic diseases can be malignant—cancerous—or benign—not cancerous. The following are some types of GTD:
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Hydatidiform mole, or molar pregnancy. This is the most common type of GTD. In about one out of every five women it will become malignant. There are two types of molar pregnancies. The first type is a complete mole. Usually, it is not related to a fetus and consists of only an abnormal placenta. In rare cases, it can be part of a twin pregnancy. The “twin” is a normal fetus and placenta.
The second type of molar pregnancy is a partial mole. It is associated with an abnormal fetus that cannot survive. Partial molar pregnancies are less likely to become malignant.
Both types of molar pregnancies have abnormal placentas. They are made up of grape-like cysts and look like “Swiss cheese” on ultrasound. Neither partial nor complete moles spread outside the uterus. They are not cancerous. They can become cancer, though. So if you have a hydatiform mole you need to be followed carefully. That will include frequent checks of the levels of pregnancy hormone—beta hCG.
The main treatment is to remove the molar placental tissue from the uterus. This is done with a D & C. An OB/GYN usually does this. A hysterectomy can also serve as treatment if a woman does not want to get pregnant in the future. After treatment, the beta hCG levels are followed until they become negative. If you are treated for this type of GTD, you’ll need some form of reliable birth control. It’s important not to get pregnant for at least 6 months after treatment.
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Invasive mole. The myometrium is the muscular wall of the uterus. It can be invaded by an abnormal placenta from a hydatidiform mole. When that happens, it’s called an invasive mole. Sometimes, this can be seen on ultrasound or MRI.
If the invasive placenta grows a lot in the uterine wall, it can cause severe bleeding. A D & C at this point can cause a hole in the uterus or worse bleeding. The hole is called perforation of the uterus. Sometimes the invasive cells will die off and go away without treatment. In most cases, though, chemotherapy is used for treatment. If the woman does not want to become pregnant in the future, another possible treatment is a hysterectomy.
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Persistant gestational trophoblastic disease. If the tumor from an invasive mole has grown deep in the uterus wall, it cannot be removed with a simple D & C. Such a mole is called persistent gestational trophoblastic disease.
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Quiescent gestational trophoblastic disease. This is a form of persistent GTD that is “quiet.” That means it is not actively dividing. The diagnosis is suspected when the hCG tests stay at a moderate to low level without further drop. This can occur even with chemotherapy.
Special blood tests can help determine whether a tumor is in a quiet or “quiescent” state. If it is, more chemotherapy is not likely to help. Ten to 20% of these quiet tumors will reactivate. When they do, they become aggressive again. At that point a woman will need chemotherapy or another special treatment.
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Choriocarcinoma. This is a very malignant—ancerous—type of GTD. These malignant placental tumor cells grow faster than hydatiform moles. They will attack blood vessels early. That means it is more likely to spread to other organs such as lung, liver, and brain.
These cancerous cells are very fragile and very likely to bleed. They may not be diagnosed before a life threatening event such as bleeding in the brain or liver happens. Choriocarcinomas are usually only related to pregnancy and do not grow in other areas of the body. They can be very difficult to manage and are best handled by experts.
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Placental-site Trophoblastic Tumor (PSTT). PSTT is a very rare form of GTD. It grows in the layers where the placenta attaches to the uterus. It is caused by a special placenta or trophoblastic cell called an intermediate trophoblast cell. These cells make very little hCG. As a result, the pregnancy hormone is usually very low or negative.
These tumors usually remain within the uterus. They are often diagnosed at the time of a hysterectomy. PSTT does not respond to chemotherapy and must be removed by surgery. If it spreads, it is very difficult to treat and should be managed by experts in a Trophoblastic Center.
