Genetic origin of malignant trophoblastic neoplasms.

The genetic origin of three trophoblastic neoplasms (two choriocarcinomas and a placental site trophoblast tumor (PSTT)] was determined by analysis of the restriction fragment length polymorphism (RFLP) pattern. One choriocarcinoma, which was believed not illogically to have developed from an antecedent complete mole, contained both paternal and material RFLP alleles and thus was probably the product of a normal fertilization. The other choriocarcinoma was not of gestational origin but had RFLPs homozygous at some loci and heterozygous at others, compatible with the parthenogenic origin of this tumor from a germ cell after meiosis I. The PSTT required amplification of DNA sequences by polymerase chain reaction (PCR) because of the small amount of tumor material available. This tumor contained RFLP alleles from both parents and appeared to have resulted from a previous unrecognized (and abnormal) pregnancy.