Endometrial Stromal Expression of ER, PR, and B-Catenin Toward Differentiating Hyperplasia Diagnoses

Background. The interpretation of histopathological changes of endometrial hyperplasia with or without atypia can be challenging. We aim to investigate the role of specific immunohistochemical markers in the endometrial stroma to classify endometrial hyperplasia in difficult cases. Methods and Results. We retrospectively reviewed and reclassified (WHO 2014): 47 specimens with endometrial hyperplasia without atypia, 33 with atypical hyperplasia (AH), and 13 endometrioid adenocarcinomas. We performed IHC for B-catenin, E-cadherin, p16, estrogen receptors and progesterone receptors, and B-cell lymphoma 2 (BCL2). Percentage of positive stromal cells was calculated. B-catenin was equally expressed in the stroma of both hyperplasia and AH (mean 60%, 50%; P = .17) and was absent from adenocarcinoma (0%, hyperplasia vs adenocarcinoma; P < .0001, AH vs adenocarcinoma; P < .0001). E-cadherin was not expressed in the stroma of any lesion, while p16 expression levels were not statistically different (hyperplasia vs AH; P = .46, hyperplasia vs adenocarcinoma; P = .22, AH vs adenocarcinoma; P = .48). Estrogen and progesterone were highly identified in stromal cells of hyperplasia (80%) and diminished in AH (respectively, at 30% and 60%, hyperplasia vs AH; P < .0001), and in adenocarcinoma (0% and 40%, respectively). Finally, BCL2 was not differentially expressed (hyperplasia vs AH; P = .33, hyperplasia vs adenocarcinoma; P = .17, AH vs adenocarcinoma; P = .36). Conclusion. Estrogen and progesterone were strongly expressed in stroma exclusively of hyperplasia, while B-catenin was particularly expressed in hyperplasia and AH. Use of these markers can be useful in the differential diagnosis of hyperplasia from AH, and AH from adenocarcinoma in challenging cases.