COMPLETE HYDATIDIFORM MOLE IN TWIN PREGNANCY - DIFFERENTIATION FROM PARTIAL MOLE WITH INTERPHASE CYTOGENETIC AND DNA CYTOMETRIC ANALYSES ONPARAFFIN-EMBEDDED TISSUES

Six cases of hydatidiform mole associated with normal chorionic villi and a normal embryo/fetus (in five cases) were investigated with inter phase cytogenetic and DNA cytometric analyses for diagnostic purposes. DNA probes specific for the pericentromeric regions of chromosomes 1 and X and for the long arm of chromosome Y were used, In four cases a dizygotic twin pregnancy could be proven, In these cases, the histolog ically normal chorionic villi showed an XY DNA-diploid pattern, consis tent with a normal male conceptus, and the molar chorionic villi a XX pattern. In the other two cases an identical sex chromosomal pattern w as found in the normal and in the molar villi (XX/XX and XY/XY respect ively). In all six cases the molar placental tissues showed prominent trophoblastic hyperplasia with DNA-polyploidy, consistent with a compl ete hydatidiform mole, In two cases persistent gestational trophoblast ic disease developed, It is emphasized that twin pregnancies composed of a normal conceptus and a complete mole have a relatively high risk for the development of persistent trophoblastic disease and therefore, should be carefully differentiated from triploid partial moles with a relatively low risk of persistent gestational trophoblastic disease, These case reports indicate that additional interphase cytogenetic and DNA cytometric analyses are useful in this differential diagnosis.