OBJECTIVETo investigate the clinical utility of short tandem repeats(STR) genotyping technique for diagnosis of partial hydatidiform moles (PHM).

METHODSTen cases with the original diagnosis of PHM and six cases diagnosed as "favour PHM" or "abnormal villous, PHM not excluded" were selected for the study. The clinical information and follow-up data were reviewed. Histopathologic features were evaluated along with p57 immunohistochemistry. After DNA extraction from each sample, genotyping was performed by AmpFlSTR(®) Identifiler™ PCR kit to amplify 15 STR polymorphism loci plus the amelogenin gender-determining in a single robust PCR.

RESULTSThe age of patients ranged from 18 to 49 years (mean=29 years, median=29 years). Two villous populations (7/16), irregular villous contour (13/16), at least moderate trophoblastic hyperplasia (2/16), cistern formation (8/16), syncytiotrophoblastic knuckles (14/16), trophoblastic pseudoinclusions (6/16) and nucleated fetal red blood cells (8/16) were presented in these cases. Of the cases in the study, STR genotyping identified 4 monospermic complete hydatidiform moles (MCM), 3 dispermic partial hydatidiform moles (DPM) and 9 hydropic abortions (HA). The misdiagnosis rate was 13/16 only relied on morphology evaluation. Immunostaining of p57 showed 3/4 of MCM were focally positive (<5%-20%+), 1/4 of MCM were diffusely positive (70%+), 3/3 of DPM were diffusely positive (≥50%+), 7/9 of HA were diffusely positive (≥50%+), and 2/9 of HA were focally positive (10%+).

CONCLUSIONSCombination of histomorphologic evaluation and p57 immunostaining is insufficient for a definitive diagnosis of PHM. STR genotyping offers an accurate diagnosis of PHM.