Exploring the influence of adenomyosis on endometrial cancer

OBJECTIVES: To evaluate whether coexisting adenomyosis is associated with distinct clinicopathological features in women with endometrial cancer. STUDY DESIGN: This retrospective cohort included 399 women who had undergone hysterectomy for histologically confirmed endometrial carcinoma at a tertiary center between 2016 and 2024. Patients were stratified according to the presence or absence of adenomyosis on final pathology. Clinical and pathological characteristics were compared, and multivariable logistic regression was used to adjust for potential confounders. MAIN OUTCOME MEASURES: Associations between adenomyosis and tumor invasiveness, stage at diagnosis, and other pathological features. RESULTS: The cohort consisted predominantly of postmenopausal women, with a median age of 67 years. Adenomyosis was identified in 94 patients (23.6%). Women with adenomyosis were more likely to have non-invasive tumors (1.1% vs. 6.8%; p = 0.037) and early-stage disease (Stage I-II: 91.3% vs. 80.8%; p = 0.029). After adjustment for age, adenomyosis was associated with lower odds of advanced-stage disease (adjusted odds ratio 0.40; 95% confidence interval 0.17-0.91). In a comprehensive model including age, histologic subtype, and peritoneal cytology, this association remained significant (adjusted odds ratio 0.20; 95% confidence interval 0.05-0.78). Endometrioid histology was independently protective (adjusted odds ratio 0.32; 95% confidence interval 0.13-0.75), while positive cytology was linked to advanced-stage disease (adjusted odds ratio 4.40; 95% confidence interval 1.86-10.40). CONCLUSIONS: Coexisting adenomyosis is associated with less invasive tumors and a lower likelihood of advanced-stage endometrial cancer. These findings suggest adenomyosis may influence tumor progression, potentially through structural or biological mechanisms. Prospective studies are needed to clarify the underlying biology and long-term prognostic impact. TRIAL REGISTRATION: This study was performed in line with the principles of the Declaration of Helsinki. Approval was granted by the Ethics Committee of Rabin Medical Center (Date 3 July 2025 /No RMC- 0037-25).