[Trophoblastic hyperplasia and placental carcinomas]

The mechanism instigating triploidy is linked to placental aspects. When 2 of 3 gametes are paternal in origin, molar pregnancy results, while if 2 of 3 gametes are of maternal origin the placenta is normal (15% of cases). Hydatidiform mole and chorioadenoma destruens or invasive mole are indistinguishable one from the other in terms of clinical appearance, histology and course of disease, and are always benign. Their karyotype is 46,XX (except for 3% which are 46,XY) completely paternal in origin and usually homozygotes. Trophoblastic carcinoma however is aneuploid and heterozygotic which emphasizes its allograft nature i.e. with no apparent relationship to hydatidiform mole.