Prevalence of Partial Hydatidiform Mole in Products of Conception From Gestations With Fetal Triploidy Merits Reflex Genotype Testing Independent of the Morphologic Appearance of the Chorionic Villi

Diagnosis of first-trimester partial mole is challenging as the key morphologic features may not be well-developed and may overlap with those of a nonmolar gestation harboring a cytogenetic disorder or degenerative changes. Genotype testing has emerged as the reference tool to distinguish partial mole (diandric triploid genotype) from its nonmolar mimics. However, observer variation in defining the minimum threshold of how much morphologic alteration is required to trigger genotype testing may result in a subset of partial moles that go undetected. We hypothesized that the results of fetal aneuploidy testing performed for prenatal screening or evaluation of miscarriage may assist with triggering molecular testing in the evaluation of products of conception, specifically if fetal triploidy is detected. Gestations with fetal triploidy are either a partial mole (diandric triploidy) or are nonmolar (digynic triploidy). The aims of this study were to define the prevalence of partial mole in 20 products of conception specimens with known fetal triploidy by performing genotype testing and then to determine how well established morphologic criteria for partial mole correlate with the genotype results in this setting. Genotype testing demonstrated that 65% (13/20) were a partial mole and the remainder were nonmolar digynic triploid gestations. Most partial moles were under 9 weeks gestational age and, as expected, lacked classic well-developed morphologic features. Nearly a third (4/1...
Source: The American Journal of Surgical Pathology - Category: Pathology Tags: Original Articles Source Type: research