Impact of molecular and histopathological findings on FIGO 2009 stage I endometrial cancer: Transition to FIGO 2023 staging system

Abstract Aim This study aims to investigate the impact of integrating molecular and histopathological findings into the revised International Federation of Gynecology and Obstetrics (FIGO) 2023 staging system on patients initially diagnosed with stage I endometrial cancer (EC) according to the FIGO 2009 criteria. Methods A cohort of 197 EC patients, initially classified as stage I under FIGO 2009, underwent restaging based on the updated FIGO 2023 criteria. The patients' molecular and histopathological characteristics were documented, and their impact on upstaging was analyzed. Results Molecular profiling was conducted for 81.2% (160/197) of the patients, revealing that 55.3% (109/197) were classified as non‐specific molecular profile, 14.7% (29/197) as mismatch repair deficiency, 11.2% (22/197) as p53 abnormality (p53abn), and 18.8% (37/197) as unknown. Upstaging was identified in 26.9% (43/160) of the 160 patients with known molecular profiles. Among the upstaged patients, 51.2% experienced upstaging due to p53 abnormality, 20.9% due to substantial lymphovascular space invasion (LVSI), 20.9% due to aggressive histological types, and 6.9% due to high grade. Conclusions The introduction of the molecular profile into the revised FIGO 2023 staging system for stage I EC has led to notable changes in the staging of approximately one‐fifth of patients. While p53 abnormalities have emerged as the most influential factor contributing to the upstaging, LVSI and aggressive histological types also represent significant contributing factors.