Interobserver Variability in the Diagnosis of Uterine High-Grade Endometrioid Carcinoma

Abstract

Context.—Low interobserver diagnostic agreement exists among high-grade endometrial carcinomas. Objective.—To evaluate diagnostic variability in International Federation of Gynecology and Obstetrics (FIGO) grade 3 endometrioid adenocarcinoma (G3EC) in 2 different sign-out practices. Design.—Sixty-six G3EC cases were identified from pathology archives of Wayne State University (WSU, Detroit, Michigan) (general surgical pathology sign-out) and 65 from Memorial Sloan Kettering Cancer Center (MSK, New York, New York) (gynecologic pathology focused sign-out). Each case was reviewed together by 2 gynecologic pathologists, one from each institution, and classified into the G3EC group or a reclassified group. Clinicopathologic parameters were compared. Results.—Twenty-five WSU cases (38%) were reclassified as undifferentiated (n = 2), serous (n = 4), mixed endometrioid and serous carcinomas (n = 12), and FIGO grade 2 endometrioid adenocarcinomas with focal marked nuclear atypia (n = 7). Eleven MSK cases (17%) were reclassified as undifferentiated (n = 5), serous (n = 1), mixed endometrioid and serous carcinomas (n = 4), and mixed endometrioid and clear cell carcinomas (n = 1). Agreement rate between original and review diagnosis was 83% (54 of 65) at MSK and 62% (41 of 66) at WSU (P = .01) with an overall rate of 73% (95 of 131). There were more undifferentiated carcinomas at MSK than there were at WSU (45% [5 of 11] versus 8% [2 of 25]; P = .02). There were more grade 2 endometrioid adenocarcinomas with focal, marked nuclear atypia at WSU (28%; 7 of 25) than there were at MSK (0%) (P = .03). Mixed endometrioid and serous carcinoma was the most common misclassified subtype (44%; 16 of 36). Conclusion.—Moderate interobserver variability exists in the diagnosis of G3EC with a significantly greater diagnostic agreement rate in gynecologic pathology–focused sign-out than in general sign-out practice.