[The propensity to malignant changes in heterozygous moles]

There are at least two mechanisms of origin for complete mole, each with different genetic implications; 1) the fertilization of an empty egg by a haploid sperm and its subsequent duplication (homozygous mole), 2) the fertilization of such an egg by two haploid sperms, which produces an heterozygous constitution of allelic genes (heterozygous mole). The present study was undertaken to investigate whether the difference of origin would determine whether the moles underwent malignant transformation or not. By using of chromosomal, enzymatic and HLA polymorphisms, 35 moles were confirmed to be androgenetic in origin. Among them fifteen homozygous and 4 heterozygous moles were identified. The persistency of high HCG titration of the urine in the mother was observed in all 4 cases from the latter (4/4-100%), though the percentage of the development of sequelae in the former was low (1/15-6.7%). The diagnosis of destructive mole was established in the uterine lesion of 2 heterozygous moles by pathological examination. These two patients had lung metastases. A high incidence of sequelae after the expulsion of heterozygous moles suggests that the heterozygous constitution of allelic genes plays an important role in the process of malignant transformation of trophoblasts.