Determining the Inter- and Intraobserver Reproducibility of the Diagnosis of Endometrial Hyperplasia Subgroups and Well-Differentiated Endometrioid Carcinoma in Endometrial Curettage Specimens

Background: Many studies have attempted to identify histologic features that help to distinguish atypical hyperplasia from hyperplasia without atypia and well-differentiated endometrioid carcinoma of the endometrium; however, few have evaluated the reproducibility of these diagnoses. Methods: Five pathologists independently reviewed 100 endometrial curettage specimens chosen to represent the spectrum of proliferative lesions of the endometrium. This included simple hyperplasia, complex hyperplasia, atypical hyperplasia, and well-differentiated endometrioid carcinoma. Slides were reviewed once for interobserver agreement among the five pathologists and twice for intraobserver agreement by one of them. Results: The results were assessed using the weighted kappa statistic. The mean intraobserver kappa value was 0.86. The mean interobserver kappa values by diagnostic category were as follows: simple hyperplasia without atypia: 0.74; complex hyperplasia without atypia: 0.33; atypical hyperplasia: 0.34, and well-differentiated endometrioid carcinoma: 0.64; with a kappa value of 0.53 for all cases combined. Conclusion: A major interobserver discrepancy exists in the diagnosis of complex and atypical hyperplasia which are the most similar mimics of endometrioid carcinoma.