P57Kip2 immunohistochemical staining and flow cytometry ploidy analysis of hydatidiform moles and hydropic abortions

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The prognosis and the optimum clinical management of hydropic gestation cases rely principally on accurate diagnosis of molar pregnancy subtypes and their distinction from nonmolar hydropic abortus (HA), which is sometimes difficult and uncertain by histopathology.


The aim of this article was to perform P57Kip2 immunohistochemical staining and flow cytometry (FCM) ploidy analysis of molar and nonmolar aborted gestations and to assess whether these ancillary techniques combined with histomorphology would refine the diagnosis.

Materials and methods

The study included 15 complete hydatidiform moles (CHMs), 15 partial hydatidiform moles (PHMs), and 12 HA. Four-micrometer-thick section from each case was immunostained with a monoclonal antibody to P57Kip2 protein, a paternally imprinted cell cycle inhibitor gene. Sections of 50 µm thickness from each case were submitted for analysis of DNA ploidy and S-phase fraction using FCM.


Initial results showed that all CHM cases were P57Kip2 negative, whereas all HA cases and 13/15 PHMs exhibited positive P57Kip2 expression. Most of the CHM (93.4%) cases were diploid and 6.6% were tetraploid. Eight (53.3%) PHM specimens were diploid and seven (54.7%) were triploid. The majority (75%) of HA were diploid. On histopathological re-evaluation, one of three triploid/P57-positive HA was reclassified as PHM. Three of seven diploid/P57-negative PHMs changed to CHM. Finally, the overall diagnosis was changed in four (∼10%) cases.


Current study shows that P57-negative expression identifies CHM cases, whereas FCM may aid in distinguishing PHMs from HAs. Hence, ancillary techniques can improve the diagnosis of hydropic gestations in morphologically equivocal cases.

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