Soheila Sarmadi - Associate Professor of Pathology, Department of Pathology ,Yas Hospital, Tehran University of Medical Sciences,Tehran,Iran
Narges Izadi-Mood - Professor of Pathology ,Department of Pathology, Yas Hospital, Tehran University of Medical Sciences,Tehran,Iran.
Dorna Motevalli - Resident of Pathology ,Sina Hospital, Tehran University of Medical Sciences, Tehran,Iran

Background:Not uncommonly, the pathologist has to differentiate complete hydatidiform mole (CHM) from partial hydatidiform mole (PHM) or hydropic abortion (HA), when encountering hydropic villi in product of conception specimens. It is important to distinguish CHM from PHM, as the former has greater malignant potential and, consequently, requires stricter patient management and follow-up. The histological diagnostic criteria are subjective and demonstrate considerable interobserver variability. This study assessed diagnostic inter- and intra-observer variability of hydatidiform mole and histological criteria between two pathologists. Methods: We retrospectively studied 90 specimens of abortus conception. 1-3 hematoxylin and eosin-stained slides from each case was given independently to the pathologists asked to make the diagnosis of CHM, PHM or HA. In order to evaluate the intra-observer agreement rate, each pathologist blindedly reviewed the same slides 6 months later. Kappa value was calculated for the inter- and intra-observer agreement in the first and second rounds. Results: Of the total 36.7% disagreement (kappa=0.403 moderate) between two pathologists, 24.4% and 12.2%, respectively, related to differentiating PHM from CHM ( kappa=0.444 moderate ) and PHM versus HA. The intra-observer agreement regarding the distinction of CHM from HA was almost perfect for both pathologists (kappa=1 and 0.960 almost perfect) (p value=0.000). Conclusion: These results mean that the reported histological criteria are not being consistently applied and the difference in diagnostic agreement rates in existing studies may imply that each center needs to evaluate its own inter-observeragreement rate and attempt to improve it.

Complete hydatidiform mole, partial hydatidiform mole, hydropic abortion, intraobserver variability, inter-observer variability, histological criteria