DNA Genotyping of Suspected Partial Hydatidiform Moles Detects Clinically Significant Aneuploidy

The diagnosis of partial hydatidiform mole (PM) is especially difficult early in gestation as the morphology of nonmolar abortus (NMA) may mimic PM. Molecular genotyping analysis can definitively identify diandric triploidy, the genetic basis for PM, whereas NMA cases show a biparental inheritance. This 4-year retrospective study sought to determine what proportion of NMA cases which were initially suspected as being PM was aneuploid, and whether this knowledge of aneuploidy status is clinically useful. Cases with atypical villous morphology on histopathology suggestive of PM were subjected to molecular genotyping. The genotyping testing panel contained 19 highly polymorphic short-tandem repeat markers on chromosomes 13, 18, 21, X, and Y and 2 nonpolymorphic markers for sex determination. Informative molecular genotyping analysis was available in 127 cases (56 PMs and 71 NMAs). Aneuploidy was detected in 15/71 of NMAs (21.1%): 7 cases of trisomy 18, 3 of trisomy 13, 1 of trisomy 21, and 4 of monosomy X. It is concluded that most cases of aneuploid NMAs (11/15) detected by molecular genotyping analysis of atypical villous morphology cases are sporadic in type with a low or age-related recurrence risk. Nevertheless, this information may be useful in subsequent counseling and in women undergoing in vitro fertilization by directing preimplantation genetic diagnosis in subsequent cycles. In about a quarter of aneuploid NMAs (4/15) specific aneuploidy types which may be caused by unbalanced familial chromosome rearrangement are identified and are clinically important to patient management. Detection of clinically relevant aneuploidy in NMAs represents an important secondary benefit to the adoption of molecular genotyping analysis in suspected PM.