Pelvic MRI in Endometrial Cancer Staging: A Retrospective Evaluation of the Impact of FIGO 2023

: Background The 2023 International Federation of Gynecology and Obstetrics (FIGO) staging system for endometrial cancer (EC) integrates histopathologic and molecular variables that may be inapparent at imaging. Purpose To evaluate the impact of the updated FIGO 2023 staging system on preoperative MRI assessment in patients with EC, and to assess its impact on patient outcomes. Materials and Methods In this dual-center retrospective study, women with biopsy-proven EC underwent abdominal MRI. Radiologic FIGO (rFIGO) 2009 stage was assigned from MRI and biopsy grade and histotype. Surgical specimens provided pathologic FIGO (pFIGO) 2009 and 2023 stages, incorporating molecular status. Concordance and causes of discordance were assessed. Potential impact on initial management was inferred using 2025 European Society of Gynaecological Oncology-European Society for Radiotherapy and Oncology-European Society of Pathology guidelines. Disease-free survival (DFS) and overall survival (OS) were assessed with Kaplan-Meier. Results A total of 231 women (median age, 63 years; IQR, 55-73 years) were evaluated. Major-stage agreement decreased from 86.6% (200 of 231) of patients for rFIGO 2009 versus pFIGO 2009 to 76.2% (176 of 231) for rFIGO 2023 versus pFIGO 2023 (P < .001); substage concordance declined from 74.0% (171 of 231) with FIGO 2009 to 56.3% (130 of 231) with FIGO 2023 (P < .001). Under FIGO 2023, the most common causes of discordance were minimal myometrial invasion (37 of 101 women, 36.6%), lymph node involvement (18 of 101 women, 17.8%), and histology-dependent factors such as lymphovascular space invasion (12 of 101 women, 11.9%) and histologic changes (19 of 101 women, 18.8%). Molecular data reclassified 35 of the 231 (15.2%) patients (18 patients were downstaged; 17 were upstaged). Discrepancies would have altered the initial approach in 22 of the 231 (9.5%) patients. Recurrence and death occurred in 18 (7.8%) and 16 (7.0%) of the 231 patients, respectively, with DFS and/or OS stratification across radiologic and pathologic 2009 and 2023 stages (all P < .001). Conclusion The 2023 FIGO update reduced substage concordance between preoperative pelvic MRI and final pathology, primarily due to the missed detection of minimal myometrial invasion and micrometastatic lymph node involvement. © RSNA, 2026 Supplemental material is available for this article. See also the editorial by Kataoka and Himoto in this issue.