Clinical Characteristics and Exploratory Association With Chronic Endometritis in Reproductive-Aged Women With Hysteroscopically Suspected Interstitial or Tubal Ostial Polypoid Lesions: A Retrospective Case–Control Study

To characterize the clinical features of hysteroscopically suspected polypoid lesions at the interstitial segment or tubal ostium and to explore their association with chronic endometritis (CE). In this single-center retrospective case–control study, we enrolled 485 reproductive-aged women who underwent hysteroscopy, endometrial biopsy, and immunohistochemical evaluation at the Third Affiliated Hospital of Guangxi Medical University (The Second People's Hospital of Nanning) between June 2024 and May 2026, including 97 women with hysteroscopically suspected interstitial or tubal ostial polypoid lesions and 388 controls. Univariable and multivariable logistic regression analyses identified clinical factors associated with suspected lesions, and sensitivity analyses using alternative operational definitions of CE were performed to assess the robustness of the primary findings. Women with hysteroscopically suspected interstitial or tubal ostial polypoid lesions were younger than controls [median 33.00 (IQR 30.00–36.00) vs. 35.00 (31.00–38.00) years, P = 0.010] and had a higher BMI [22.89 (20.93–25.10) vs. 22.10 (20.23–24.44) kg/m 2 , P = 0.018]. The distributions of gravidity, parity, and number of induced abortions also differed significantly between groups (all P < 0.05). Concomitant endometrial polyps were more frequently detected in the suspected-lesion group than in controls (87.6% vs. 71.1%, P < 0.001), whereas cesarean scar diverticula were less frequent (5.2% vs. 16.2%, P = 0.005). The prevalence of chronic endometritis defined by CD138 positivity was 27.8% in the suspected-lesion group and 26.5% in controls, with no significant between-group difference ( P = 0.798). In the fully adjusted exploratory model, concomitant endometrial polyps (adjusted odds ratio [aOR] = 3.35, 95% CI: 1.67–7.22, P = 0.001) and intrauterine adhesions (aOR = 2.35, 95% CI: 1.39–3.99, P = 0.001) were positively associated with suspected lesions, while gravidity was inversely associated (aOR = 0.74, 95% CI: 0.60–0.91, P = 0.007). No statistically significant association was observed between CD138 positivity and suspected lesions (aOR = 0.76, 95% CI: 0.44–1.29, P = 0.317). Sensitivity analyses using alternative operational definitions of chronic endometritis yielded broadly consistent estimates in direction and magnitude. In this study, endometrial CD138 positivity was not significantly associated with hysteroscopically suspected polypoid lesions of the interstitial segment or tubal ostium. Concomitant endometrial polyps and intrauterine adhesions were positively associated with suspected lesions. These findings suggest co-occurrence of suspected lesions with local intrauterine structural abnormalities, but do not establish causality or pathogenesis. Because the study population was highly selected, the findings should not be generalized to the general reproductive-aged population or to all women with infertility.