Gestational trophoblastic disease is a pregnancy-related condition that can occur in the uterus after conception. The term gestational trophoblastic disease (GTD) actually describes a group of rare diseases that begin in the tissues that are created after conception, i.e., the joining of egg and sperm in the uterus. GTD is so named because the disease begins in the trophoblast, the layer of cells that surrounds the newly formed embryo.

Some types of gestational trophoblastic disease can develop into cancer, which is why it’s important that they be diagnosed as early as possible. With prompt diagnosis and proper treatment, the various forms of this disease can often be cured.

Since GTD can recur after treatment, it’s important to have follow-up exams on a regular basis.

Types of Gestational Trophoblastic Disease

• Hydatidiform mole (also known as molar pregnancy): While this is the most common form of GTD, it’s still relatively rare, occurring in about 1 of every 1,500 pregnancies. The sperm and egg join, but instead of developing into a fetus, the resulting tissue resembles grape-like cysts. Hydatidiform moles are benign (non-cancerous) but have the potential to develop into cancer. There are two types:
  • A complete hydatidiform mole develops when a sperm fertilizes an “empty” egg (one that contains no nucleus or DNA). All the genetic material comes from the father’s sperm. Therefore, there is no fetal tissue. About 1% to 3% of complete moles may develop into choriocarcinoma, a malignant form of GTD (read more about choricarcinoma below).
  • A partial hydatidiform mole develops when two sperm fertilize a normal egg. These contain some fetal tissue, but no viable fetus is formed. Partial moles rarely develop into malignant GTD.
• Invasive mole (or chorioadenoma destruens): This is a malignant form of hydatidiform mole that enters the myometrium (muscular wall of the uterus) and may cause the uterus to bleed. In some cases, these invasive moles result after a complete mole has been scraped away from the uterus via surgery. When an invasive mole is not cured through treatment, it is often called persistent gestational trophoblastic disease.  
• Choriocarcinoma: This is a malignant form of GTD that most often forms from a complete hydatidiform mole. It can also begin in tissues that remain in the uterus after a normal pregnancy, after a fetus is lost early in pregnancy, or after an abortion. Although rare – occurring only in one pregnancy out of 20,000 to 40,000 in the U.S. -- choriocarcinoma is a serious cancer that is likely to spread to organs beyond the uterus.  
• Placental-site trophoblastic disease: This very rare type of malignant GTD starts in the uterus where the placenta was attached. Most of these tumors do not spread to other sites in the body, but some may penetrate the muscle layer of the uterus.

Read more about Gestational Trophoblastic Disease

• Risk Factors & Symptoms
• Diagnosis & Staging
• Treatment Options

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