Role of P57KIP2 Immunohistochemical Expression in Histological Diagnosis of Hydatidiform Moles

Purpose: To determine the significance of P57KIP2 immunohistochemistry expression in the histopathological diagnosis of hydatidiform mole. Materials and Methods: Hydatidiform mole patients at King Chulalongkorn Memorial Hospital between January 1999 and December 2011 were recruited. Two gynecologic pathologists reviewed histopathologic slides to confirm diagnosis. Formalin-fixed, paraffin-embedded tissue sections were stained using a bstandard immunostaining system with monoclonal antibodies against P57KIP2 protein. Correlations among pathological features, immunohistochemical expression and clinical data were analyzed. Results: One hundred and twenty-seven hydatidiform mole patients were enrolled. After consensus review, 97 cases were diagnosed as complet (CHM) and 30 cases as partial (PHM). Discordance between the first and final H and E diagnoses was found in 19 cases (14.9%, k= 0.578). Significant pathological features to classify the type of hydatidiform mole are central cisterns, trophoblastic proliferation, trophoblastic atypia, two populations of villi, fetal vessels and scalloped borders. After performing immunohistochemistry for P57KIP2, 107 cases were P57KIP2 negative and 20 cases positive. Discordant diagnoses between final H and E diagnosis and P57KIP2 immunohistochemistry was identified in 12 cases (9.4%). Sensitivity of final H and E diagnosis for CHM was 89.7%; specificity was 95.0%. PHM sensitivity and specificity of final H and E diagnosis was 95.0% and 89.7%, respectively. Conclusions: Histopathological diagnosis alone has certain limitations in accurately defining types of hydatidiform mole; P57KIP2 immunohistochemistry is practical and can be a useful adjunct to histopathology to distinguish CHM from non-CHM.