During an 8-year period, 76 post-hysterectomy women with endometrial cancer were referred to our institution for evaluation or treatment, and had slides from the hysterectomy specimen sent for review at the request of the gynecologic oncologist (interinstitutional consultation). The original diagnosis was retrospectively compared to the review diagnosis and discrepancies were recorded. The most frequent discrepancy, identified in 24 (31.6%) of the 76 cases, involved assessment of myometrial invasion; 19 of these 24 had an original diagnosis of inner or middle third myometrial invasion and a review diagnosis of no myometrial invasion. The main reason for this discrepancy was irregularity of the endomyometrial junction, or, less commonly, extension of tumor into superficial adenomyosis. Additional discrepancies noted in 11 (14.4%) of the 76 cases included: 1) histologic tumor classification in 6 (7.9%); 2) assessment of angiolymphatic space invasion in 2 (2.6%); 3) identification of metastatic carcinoma in 1 (1.3%); and 4) change in diagnosis from adenocarcinoma to complex atypical hyperplasia and atypical polypoid adenomyoma in 1 each (2.6%). A significant subgroup of patients in this series had modifications in diagnosis; the most frequent discrepancy involved overdiagnosis of myometrial invasion, underscoring the difficulty sometimes encountered in this determination.