AimsDiagnostic separation of diandric triploid gestation, i.e. partial mole from digynic
triploid gestation, is clinically relevant, as the former may progress to postmolar
gestational trophoblastic neoplasia. The aim of the study was to investigate if the
combination of abnormal histology combined with ploidy analysis-based triploidy is
sufficient to accurately diagnose partial mole.Methods and ResultsA genotype-phenotype
correlation study was undertaken to reappraise histological parameters among 20 diandric
triploid gestations and 22 digynic triploid gestations of comparable patient age,
gestational weeks, and clinical presentations. Two villous populations, irregular
villous contours, pseudoinclusions, and syncytiotrophoblast knuckles, were common
in both groups. Villous size >= 2.5 mm, cistern formation, trophoblastic hyperplasia,
and syncytiotrophoblast lacunae were significantly more common in the partial hydatidiform
mole. Cistern formation had the highest positive predictive value (PPV) (93%) and
highest specificity (96%) for diandric triploid gestation, although the sensitivity
was 70%. Cistern formation combined with villous size >= 2.5 mm or trophoblast hyperplasia
or syncytiotrophoblast lacunae had 100% specificity and PPV, but a marginal sensitivity
of 60%-65%. A moderate interobserver agreement (Kappa = 0.57, Gwet's AC1 = 0.59) was
achieved among four observers who assigned diagnosis of diandric triploid gestation
or digynic triploidy solely based on histology.ConclusionsNone of histological parameters
are unique to either diandric triploid gestation or digynic triploid gestation. Cistern
formation is the most powerful discriminator, with 93% PPV and 70% sensitivity for
diandric triploid gestation. While cistern formation combined with either trophoblastic
hyperplasia or villous size >= 2.5 mm or syncytiotrophoblast lacunae has 100% PPV
and specificity for diandric triploid gestation, the sensitivity is only 60% to 65%.
Therefore, in the presence of triploidy, histological assessment is unable to precisely
classify 35% to 40% of diandric triploid gestations or partial moles. Histological
parameters were reappraised among 20 diandric triploid partial moles and 22 digynic
triploid gestations. None of histological parameters were unique to either partial
mole or digynic triploidy. Villous size, cistern, trophoblastic hyperplasia, and syncytiotrophoblast
lacunae were more common in the partial hydatidiform mole (PHM). However, histological
assessment was unable to classify 35% to 40% of PHM. image
