gestational trophoblastic disease
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gestational trophoblastic disease, any of a group of rare conditions in which tumours develop in the uterus from the cells that normally would form the placenta during pregnancy. The main types of gestational trophoblastic disease include choriocarcinoma, epithelioid trophoblastic tumour, hydatidiform mole (molar pregnancy), invasive mole, and placental-site trophoblastic tumour.
The most common form of gestational trophoblastic disease is hydatidiform mole, which can be either complete (no fetal tissue is present) or partial (some fetal tissue develops). Complete hydatidiform mole occurs when a sperm fertilizes an egg cell that is devoid of genetic material. Instead of a fetus, fluid-filled villi develop within the uterus, typically forming a mass resembling a cluster of grapes. Partial hydatidiform mole occurs when two sperm fertilize a normal egg cell. Although some fetal tissue develops, it is mixed with trophoblastic tissue, and the fetus is not viable. In both forms of molar pregnancy, the abnormal growths produce and release human chorionic gonadotropin (HCG), a hormone that is also produced by normal placentas and that forms the basis of commonly used pregnancy tests. Molar pregnancies can be treated with suction dilation and curettage, a surgical procedure to remove part of the uterine lining.
In rare cases, a hydatidiform mole progresses, continuing to grow after the pregnancy is terminated (usually as a result of abortion). This condition, persistent gestational trophoblastic disease, occurs when the hydatidiform mole has penetrated into the myometrium (the muscle layer surrounding the uterus) and therefore cannot be removed surgically. Persistent gestational trophoblastic disease may take the form of a choriocarcinoma, an invasive mole, or a placental-site trophoblastic tumour. The disease may spread to other parts of the body. Invasive moles may spontaneously regress, or they may require additional treatment.
Although about half of choriocarcinomas begin as molar pregnancies, they may also occur following abortion, miscarriage (spontaneous abortion), tubal pregnancy (the ovum becomes implanted in one of the fallopian tubes), or healthy pregnancy. Likewise, placental-site trophoblastic tumours and epithelioid trophoblastic tumours can also develop following a healthy pregnancy with normal delivery. Whereas choriocarcinomas tend to metastasize (spread), however, placental-site and epithelioid tumours very rarely spread beyond the uterus.
Gestational trophoblastic disease typically is detected in relatively early stages of development, owing to the routine use of ultrasound and blood testing early in the course of pregnancy. Women with the condition may think they are pregnant because of a positive pregnancy test (the result of HCG production by the tumour). Some women also experience morning-sickness-like symptoms (nausea and vomiting), though vomiting may be more frequent than during a normal pregnancy. More-severe indications of disease include abdominal swelling (abnormal uterine enlargement for the stage of perceived pregnancy), preeclampsia (an acute hypertensive condition), and vaginal bleeding. Diagnosis typically is confirmed by imaging (e.g., ultrasound, computed tomography) and blood tests in which levels of HCG are found to be abnormally high.
In addition to the use of suction dilation and curettage, other treatment options for gestational trophoblastic disease may include chemotherapy, radiation therapy, or hysterectomy (surgical removal of the uterus). Chemotherapy frequently is curative for gestational trophoblastic disease, regardless of disease stage. In cases in which the disease has spread or is unresponsive to chemotherapy, radiation therapy may be used. Women who no longer wish to have children may consider hysterectomy, which removes local disease in the uterus but is ineffective for disease that has metastasized.