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.