Gestational Trophoblastic Neoplasia is a type of Gestational Trophoblastic Disease (GTD).
GTD is a heterogeneous group of interrelated lesions arising from the epithelium of the placenta. GTD arises from the placenta, and therefore all forms of the disease produce human chorionic gonadotrophin (hCG), a hormone produced during pregnancy, first by the embryo and later by the placenta, that aids continued progesterone production. hCG is the hormone that produces positive pregnancy tests.
GTD has several types:
- Molar pregnancy (when a non-viable fertilized egg implants in the uterus).
- Complete mole: a non-invasive tumor that results from fertilization of an empty egg by a sperm. No fetal tissues are present. Can progress to metastatic or persistent disease.
- Incomplete mole: a non-invasive tumor that results from fertilization of a normal egg by 2 sperms. Fetal tissues are present, but it is not a viable fetus.
- Persistent or Invasive GTD: once GTD persists or becomes invasive, it is considered a neoplasia. Once this occurs, it is considered a Gestational Trophoblastic Neoplasia (GTN).
GTN has three distinct subtypes:
- Invasive GTN
- Placental site trophoblastic tumors (PSTT)
The incidence of GTD varies throughout the world. The highest incidence of GTD in the world occurs in Asia, while North America has one of the lowest rates. This drastic difference in incident rates is often attributed to dietary factors, such as deficiencies in carotene, vitamin C, and animal fats.