Purpose: To investigate the histopathological association between chronic endometritis (CE) and adenomyosis, focusing onbasal endometrial alterations and the potential involvement of tissue injury and repair (TIAR) mechanisms. Methods: This retrospective case–control study included 146 propensity score- matched hysterectomy specimens (73 adenomy-osis, 73 controls). CE was diagnosed via CD38 immunohistochemical staining, identifying ≥ 5 plasma cells per high- power field.Basal endometrial thickness was measured digitally at the endo- myometrial junction. Basal endometrial loss was defined as theabsence of the basal layer in at least two of three regions. Results: CE was significantly more frequent in the adenomyosis group (23.3%) than in controls (9.6%; p 0.028). Basal endo-metrial loss, observed in 23.3% of cases, was strongly associated with CE (47% vs. 7.1%; p < 0.001). In patients with measurablethickness, a 0.15 mm cutoff predicted CE with AUC 0.888 (sensitivity 83.3%, specificity 86.9%). In multivariate analysis, basalendometrial loss was an independent risk factor for CE (adjusted OR 10.45, 95% CI 4.12–26.51; p < 0.001). Conclusions: CE is significantly associated with adenomyosis. Basal endometrial loss may mediate this relationship throughTIAR- related mechanisms, suggesting CE as a potential therapeutic target in adenomyosis