Gestational trophoblastic disease (GTD), or placental cancer, is a group of abnormal tumors that form in the tissue that would normally become the placenta, the organ that develops during pregnancy to feed the fetus. A baby may or may not develop during these types of pregnancies.
There are two types of GTD tumors:
- Hydatidiform mole (also called a molar pregnancy)
- Choriocarcinoma (a type of cancer)
If a patient has a hydatidiform mole, the sperm and egg cells have joined without the development of a baby in the uterus. Instead, the tissue that is formed resembles grape-like cysts. Hydatidiform mole does not spread outside of the uterus to other parts of the body.
There are partial molar pregnancies and complete molar pregnancies. A partial molar pregnancy means there is an abnormal placenta and some fetal development. In a complete molar pregnancy, there is an abnormal placenta but no fetus.
If a patient has a choriocarcinoma, a cancerous tumor may have started from a hydatidiform mole or from tissue that remains in the uterus following an abortion or delivery of a baby. Choriocarcinoma can spread from the uterus to other parts of the body.
A very rare type of GTD starts in the uterus where the placenta was attached. This type of cancer is called placental-site trophoblastic disease.