There are 2 main types of gestational trophoblastic disease.^[1]

Hydatidiform mole

Hydatidiform mole is the most common type of gestational trophoblastic disease. Hydatidiform mole is also called a molar pregnancy.

If a woman has a hydatidiform mole, the sperm and egg cells have joined but have not developed into a foetus. Instead, cysts are formed, which are sacs of fluid that look like grapes.

A hydatidiform mole is usually benign (not cancer), but it may spread to nearby tissues (invasive mole) or become a malignant tumour called gestational trophoblastic neoplasia.

There are 2 types of hydatidiform mole:

•      Complete – this is where there is a mass of rapidly growing abnormal cells, but no foetus.

•      Partial – this is where there is an abnormal, nonviable foetus, as well as placenta.

Gestational trophoblastic neoplasia

Gestational trophoblastic neoplasia is a type of gestational trophoblastic disease that is usually malignant – that is, it will spread from the uterus to other parts of the body.

There are 4 subtypes of gestational trophoblastic neoplasia.

Invasive moles

Invasive moles are when trophoblast cells grow into the muscle layer of the uterus. Some may need treatment, whereas others may disappear on their own without treatment.

Choriocarcinomas

Choriocarcinomas are when trophoblast cells spread to the muscle layer of the uterus and nearby blood vessels. This type of malignant tumour can also spread to other parts of the body.

Placental-site trophoblastic tumours

A placental-site trophoblastic tumour is a very rare type of gestational trophoblastic tumour that starts in the uterus where the placenta was attached. A tumour forms in the trophoblast cells and can spread to the muscle layer of the uterus and nearby blood vessels.

This is a slow-growing tumour that may only show symptoms months or years after a normal pregnancy.

Epithelioid trophoblastic tumours

An epithelioid trophoblastic tumour is a very rare subtype of gestational trophoblastic neoplasia. It can be benign or malignant. If it is malignant, it can spread to the lungs or bone.