Histopathological Association Between Chronic Endometritis and Adenomyosis: Clinical Findings and Risk Factors

To investigate the histopathological association between chronic endometritis (CE) and adenomyosis, focusing on basal endometrial alterations and the potential involvement of tissue injury and repair (TIAR) mechanisms.

This retrospective case-control study included 146 propensity score-matched hysterectomy specimens (73 adenomyosis, 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 the absence of the basal layer in at least two of three regions.

CE was significantly more frequent in the adenomyosis group (23.3%) than in controls (9.6%; p = 0.028). Basal endometrial loss, observed in 23.3% of cases, was strongly associated with CE (47% vs. 7.1%; p < 0.001). In patients with measurable thickness, a 0.15 mm cutoff predicted CE with AUC 0.888 (sensitivity 83.3%, specificity 86.9%). In multivariate analysis, basal endometrial loss was an independent risk factor for CE (adjusted OR 10.45, 95% CI 4.12-26.51; p < 0.001).

CE is significantly associated with adenomyosis. Basal endometrial loss may mediate this relationship through TIAR-related mechanisms, suggesting CE as a potential therapeutic target in adenomyosis.