Trophoblastic cells constitute the outer layer of an embryo.
Trophoblastic diseases originate during pregnancy, and consequently contain genetic material, which is foreign for the woman. The disease can occur after normal pregnancy, ectopic pregnancy, as well as spontaneous and induced abortion.
During fertilization, trophoblastic cells invade the endometrium, blood vessels and myometrium to establish fetomaternal circulation. In a normal pregnancy, a large number of trophoblasts circulate in the mother's blood system. In trophoblastic diseases, there is uninhibited invasion of trophoblasts in the mother's myometrium and blood system.
Trophoblastic diseases are separated into:
- Complete hydatidiform mole
- Partial hydatidiform mole
- Persistent trophoblastic disease/Invasive mole
- Placental-site trophoblastic tumor
- Epithelioid trophoblastic tumor
Incidence in Norway (1):
- Invasive persistent mole occurs in 0.9 cases per 1000 births, and constitutes about 50 cases per year.
- Choriocarcinoma occurs in 0.2 cases per 1000 births.
- Placenta-site trophoblastic tumor occurs once per 500,000 births, and equals about 1 case per 10 years. In 2015 there was one case in the placenta.
The incidence of trophoblastic diseases is higher in China and southeast Asia and occurs in 3 cases per 1000 births (2).