Epidemiological aspects and diagnostic accuracy of morphological diagnosis of hydatidiform mole using p57kip2 immunostain in Nnewi, South-East Nigeria – A multicenter study

Introduction: There have been numerous studies on hydatidiform mole (HM) in Nigeria, but some lacked histological diagnosis, and others did not differentiate complete hydatidiform mole (CHM) from partial hydatidiform mole (PHM). In addition, none of these studies involved immunohistochemical (IHC) diagnosis or assessed the accuracy of morphologic diagnosis of CHM. The objective of this study is to determine the epidemiology and accuracy of morphologic diagnosis of CHM using p57KIP2 IHC stain. Materials and Methods: The paraffin blocks of histologically diagnosed cases of CHM and PHM seen at two histopathology laboratories in Nnewi, South-East Nigeria, were retrieved from the archives. IHC staining for p57KIP2 was done. Results: In this study, we reviewed and reclassified 54 cases of routinely stained HMs as 15 (27.8%) CHMs and 39 (72.2%) PHMs. However, following IHC staining, we further reclassified them as 21 (38.9%) CHMs and 33 (61.1%) PHMs. Discordant histopathological diagnosis between routine staining with hematoxylin and eosin (H and E) and IHC staining with p57KIP2 was identified in eight cases (which constitutes 14.8% of the studied cases): one case was a false-positive diagnosis, while the remaining seven cases were false-negative diagnosis. Thus, the sensitivity and specificity of histopathological diagnosed cases of CHM by H and E were 66.7% and 97%, respectively, with a positive predictive value of 93.3%, negative predictive value of 82.1%, and total accuracy of 85.2%. Conclusions: Morphology alone is suboptimal for accurate diagnosis of CHM. We therefore strongly recommend the routine use of p57KIP2 immunostain in all suspected cases of HM.