Objectives Diagnosis of hydatidiform mole is improved through the use of ancillary diagnostic methods such as ploidy or genotyping. The purpose of this study was to evaluate the performance of two commonly used methods, ploidy and genotyping.

Methods The cohort consisted of 72 cases of products of conception where there was either a clinical or histologic suspicion of mola hydatidosa, where both ploidy and genotyping were attempted. Final diagnosis of the cases was made through a combination of histology, p57 immunohistochemistry, ploidy and genotyping. Ploidy analysis was performed by image cytometry. For genotyping, genomic DNA was extracted from separate microdissected fractions of maternal and fetal tissue and analyzed using the AmpFlSTR Identifiler PCR amplification kit (Applied Biosystems, Foster City, USA).

Results The final diagnosis of the 72 cases was 42 partial moles (PM), 14 complete moles (CM) and 14 non-molar gestations (NMG). Ploidy analysis was successful in 50/72 cases (70%) and genotyping was successful in 60/72 cases (83%). The most common reason for failure in ploidy analysis was difficulty in interpreting the generated ploidy curves. The most common reason for failure in genotyping was difficulty in obtaining clean, non-mixed maternal and villous material.

Conclusions In this cohort genotyping appears to be the more reliable method. Method failure was a result of a lack of clean, non-mixed, material. Careful attention to dissection is a critical lab step. The majority of POCs could be classified using both methods.