What is Gestational Trophoblastic Disease (GTD)?

Gestational Trophoblastic Disease (GTD) refers to a rare type of tumor that begins in the trophoblast cells inside the uterus during pregnancy. During a normal pregnancy, an organ called the placenta grows inside the uterus to protect, support, and nourish the growing fetus. After an egg is fertilized, cells called trophoblasts surround the growing embryo and eventually develop into the placenta over the course of a pregnancy. Gestational Trophoblastic Disease (GTD) occurs when these trophoblast cells develop abnormally and form a growth inside the uterus instead of a normal placenta and embryo. GTD can develop any time during or after a pregnancy. There are two main types of GTD:

• (1) Hydatidiform Moles / Molar Pregnancy – Usually benign
• (2) Gestational Trophoblastic Neoplasia – Usually malignant

Hydatidiform Moles / Molar Pregnancy

A hydatidiform mole, also known as a molar pregnancy, is the most common type of Gestational Trophoblastic Disease (GTD). A hydatidiform mole occurs when the tissue that normally develops into the placenta, instead develops into an abnormal growth inside the uterus that looks like a large cluster of grapes. Most molar pregnancies are benign but may develop into a cancerous condition known as “invasive mole”. A molar pregnancy can be either “complete” or “partial”. In a complete molar pregnancy, only an abnormal growth develops inside the uterus instead of the embryo and placenta. In a partial molar pregnancy, an abnormal growth develops, as well as an abnormal embryo and partial placenta.

Gestational Trophoblastic Neoplasia (GTN)

There are a few different types of Gestational Trophoblastic Neoplasia (GTN):

• Invasive mole: Some cases of molar pregnancy may eventually become an “invasive mole”. An invasive mole is a molar pregnancy in which the molar tissue can spread into nearby tissue such as the wall of the uterus. Complete molar pregnancies are more likely to become invasive moles than partial molar pregnancies.
• Choriocarcinoma: A choriocarcinoma is a malignant and very aggressive form of Gestational Trophoblastic Disease (GTD). Choriocarcinomas can develop after a molar pregnancy or after a normal pregnancy. These tumors can invade nearby tissues and structures in the pelvis and can spread to distant organs, such as the lungs, liver, or brain.
• Placental-site trophoblastic tumor (PSTT): Placental-site Trophoblastic Tumor (PSTT) is a very rare form of Gestational Trophoblastic Disease (GTD) that starts in the trophoblast cells in the area where the placenta joins to the uterus. These tumors can develop after a molar pregnancy or after a normal pregnancy. These tumors may invade nearby tissues or structures in the pelvis or spread to distant sites but are less likely to spread than choriocarcinomas. Chemotherapy is generally ineffective against these tumors, and hysterectomy is usually recommended as the primary treatment.
• Epithelioid trophoblastic tumor: Epithelioid Trophoblastic Tumors (ETTs) are also very rare. These tumors are less aggressive than choriocarcinomas and have similar behavior to PSTTs. ETTs may occasionally grow in the cervix and can be mistaken for cervical cancer.