Choriocarcinomas can follow pregnancy of any type. Hydatidiform mole, the precursor choriocarcinomas, is thought to result from the fusion of two male gametes (without the participation of an ovum). Invasive moles, choriocarcinomas, occur with a frequency of 1 in 15,000 pregnancies in the USA; there is marked geographical variation, with a 10-fold higher incidence in Southeast Asia and the Far East. Familial biparental hydatidiform mole (FBHM) is the only recessive condition that is only expressed in females.
Heterogeneity occurs; one locus was mapped to 19q13, and the responsible gene at this locus, NLRP7, was identified as the first gene that predisposed to choriocarcinomas (Murdoch et al. 2006). The protein is involved in the intracellular regulation of bacterial-induced inflammation and is a negative regulation interleukins. A second gene, C6orf221 (ECAT1), was found to be mutated in three families with FBHM (Parry et al. 2011). The phenotypes of families with mutations in ECAT1 and NLRP7 appear to be indistinguishable.