Characterisation of a rare hydatidiform mole with aberrant p57 expression

Accurate diagnosis and subclassification of hydatidiform mole (HM) are important to stratify the risk of persistent gestational trophoblastic disease (GTD) and gestational trophoblastic neoplasia (GTN). A combination of histomorphology and ancillary studies including p57 immunohistochemistry (IHC) and/or molecular genotyping by short tandem repeat analysis enable subclassification of most HM into partial hydatidiform mole (PHM) or complete hydatidiform mole (CHM). Here we report a rare HM with equivocal morphology and discordant p57 expression within individual villi and divergent p57 expression across villi. Molecular genotyping of DNA extracted from laser capture microdissected (LMD) chorionic villi allowed identification of CHM and rare androgenetic/biparental mosaicism. This study exemplifies a potential diagnostic pitfall and highlights the importance of inter-disciplinary examination such as p57 IHC and molecular genetics in the diagnosis of HMs.