Adenomyosis is associated with proliferative endometrial disorders

OBJECTIVE: To assess the prevalence of proliferative endometrial disorders in women with histologically confirmed adenomyosis and to evaluate the independent association between adenomyosis and each lesion type. DESIGN: Retrospective cohort study. SUBJECTS: Consecutive patients undergoing hysterectomy between January 2021 and August 2024, excluding those with histologically confirmed gynecological malignancies (n = 734). EXPOSURE: None. Histological and clinical records were reviewed to identify adenomyosis and coexisting endometrial disorders. MAIN OUTCOME MEASURES: Primary outcome was the prevalence of endometrial polyps, endometrial hyperplasia without atypia, and endometrial intraepithelial neoplasia in patients with histologically confirmed adenomyosis. Secondary outcome included the independent association between adenomyosis and each endometrial disorder. RESULTS: Adenomyosis was identified in 34.7% (255/734) of cases. Proliferative endometrial disorders were more prevalent among patients with adenomyosis (37.6% vs. 25.1%). In multivariable analysis, adenomyosis was independently associated with these conditions overall (aOR 1.87, 95% CI: 1.31, 2.65), including endometrial polyps (aOR 1.69, 95% CI: 1.03, 2.79), endometrial hyperplasia without atypia (aOR 2.07, 95% CI: 1.34, 3.21), and endometrial intraepithelial neoplasia (aOR 2.06, 95% CI: 1.16, 3.66). After adjustment for established clinical risk factors for endometrial cancer (obesity, menopause, nulliparity and abnormal uterine bleeding), adenomyosis remained in the predictive model for EIN. CONCLUSION: The present study identified an independent histopathological association between adenomyosis and proliferative endometrial disorders, including endometrial intraepithelial neoplasia, the lesion with the highest malignant potential. When coexisting with other risk factors, adenomyosis may contribute to a risk profile warranting targeted endometrial assessment.