Bilateral granulomatous mastitis associated with ductoscopy.

Background: Some patients with granulomatous mastitis (GLM) exhibit nipple discharge from the healthy breast. Ductoscopy was conducted on healthy breasts with discharge in these patients, and it was observed that some patients developed contralateral GLM shortly after ductoscopy. This study investigated the association between ductoscopy and GLM formation. Methods: Forty patients diagnosed with GLM who underwent ductoscopy on the healthy breast were included and divided into bilateral (10 cases) and unilateral (30 cases) groups. General and clinical data of the patients were collected, and single- and multi-factor logistic regression analyses were used to screen potential risk factors for GLM formation after ductoscopy. Results: Univariate and multivariate analyses indicated that the detection of "neutrophils and lymphocytes" (P=0.02) in ductal cytology smears was an independent risk factor for the occurrence of masses after ductoscopy. The area under the curve (AUC) for predicting the occurrence of erythema in both lower limbs after the occurrence of a mass in the contralateral breast following ductoscopy was 0.843, with a specificity of 0.853 and a sensitivity of 0.833. Conclusions: We hypothesize that ductal injury with extravasation of static inflammatory substances within the lumen promotes a local granulomatous reaction in the breast lobules, which is closely associated with the pathogenesis of GLM. Ductoscopy may simulate the pathogenesis of GLM in the subtype with mammary duct injury after breast trauma.