IntroductionGranulomatous mastitis (GM) is a chronic inflammatory breast disease. In recent years, the role of Corynebacterium in GM onset has received more and more attention. This study aims to detect the dominant bacterium in GM patients and analyze the association between clinical characteristics and infectious factors.MethodsIn this study, 88 samples from 44 GM patients, six acute lactation mastitis (ALM) patients, and 25 non-inflammatory breast disease (NIB) patients were divided into a GM pus group, a GM tissue group, an ALM pus group, and a NIB tissue group; then, 16S ribosomal DNA sequencing was used to explore their microbiota. The clinical data of all 44 GM patients were also retrospectively collected and analyzed to determine their relationship with infection.ResultsThe median age of the 44 GM patients was 33 years, and 88.6% of patients had primary-onset cases, while 11.4% were recurrences; additionally, 89.5% of patients were postpartum and 10.5% were nulliparous. The serum prolactin level was abnormal in nine patients (24.3%). Samples from 15 GM patients (34.1%) had a Corynebacterium abundance of >1% (1.08–80.08%), with eight (53.3%) displaying an abundance of >10%. Corynebacterium was the only genus with significant differences between the GM pus group and the other three groups (p < 0.05). Corynebacterium kroppenstedtii was the predominant Corynebacterium species. Among clinical characteristics, a statistical difference in breast abscess formation was observed according to Corynebacterium abundance in Corynebacterium-positive and- negative patients (p < 0.05).DiscussionThis study explored the relationship between Corynebacterium infection and GM, compared the clinical characteristics between Corynebacterium-positive and- negative patients, and provided support for the role of Corynebacterium species-in particular, C. kroppenstedtii-in the pathogenesis of GM. The detection of Corynebacterium can predict GM onset, especially in patients with high prolactin levels or a history of recent lactation.

Background Despite the rising incidence rate of granulomatous lobular mastitis (GLM), uncertainties persist about its etiologic and predisposing factors to guide clinical treatment and early prevention. The objective of this study is to explore the predisposing factors for GLM. Patients and methods This case-control study was conducted from 2018 to 2021 at Beijing Hospital of Traditional Chinese Medicine, Capital Medical University. Patients with GLM (cases) were matched with healthy examinees (controls) in a 1:1 ratio according to gender and living area. We analyzed their demographic features and investigated 75 factors that may be relevant to GLM using a standard questionnaire. Univariate and multivariable binary conditional logistic regression analyses were used to compare the differences between the two groups and evaluate the predisposing factors that may induce GLM. Results There were 594 female GLM patients and 594 matched controls included in the study. The average age of the cases was 32.78 years (mainly 20 to 40). The incidence was high within five years after childbirth, and lesions were mainly in the unilateral breast. Univariate and multivariable conditional logistic regression analyses obtained six relevant factors and six high-risk factors. The six relevant factors included age, marriage, emotional abnormality, high prolactin, psychiatric drug intake, and sex hormone intake. Additionally, the independent high-risk factors for GLM included gestation, nipple invagination, blunt trauma, non-iatrogenic massage, lactation disorder, and nipple discharge (odds ratio (OR)=17.378, 8.518, 4.887, 3.116, 2.522, 1.685, P <0.05). Menopause was an independent protective factor (OR=0.249, P <0.05). Conclusion The factors that increase milk and secretion production in the mammary duct are the main risk factors of GLM, especially when the nipples are invaginated. These factors can obstruct the duct and induce inflammation. Additionally, hormonal disorders, extrinsic trauma, and emotional abnormalities can accelerate the occurrence of GLM.

Purpose: This study aimed to explore the risk factors and clinical characteristics of granulomatous mastitis (GM) through a case-control study and establish and validate a clinical prediction model (Nomogram). Method: This retrospective study was conducted at Beijing Hospital of Traditional Chinese Medicine, Capital Medical University, Xiyuan Hospital of China Academy of Chinese Medical Sciences and Guang’ anmen Hospital, China Academy of Chinese Medical Sciences from June 2017 to December 2021. In the design of the case-control study, a total of 1634 GM patients and 186 healthy women during the same time period were included and randomly divided into the modeling group and validation group with a 7:3 ratio. To identify the independent risk factors of GM, univariate and multivariate logistic analyses were conducted and used to develop a Nomogram . The prediction model was internally and externally validated using the Bootstrap technique and validation cohort. The receiver operating characteristic (ROC) curve and the calibration curve were used to evaluate the discrimination and calibration of the prediction model. Decision curve analysis (DCA) and clinical impact curve (CIC) were utilized to evaluate the clinical significance of the model. Result: The average age of GM patients was 33.14 (mainly 20 to 40). The incidence was high within five years after delivery. It mainly occurs in the unilateral breast. Majority of the patients exhibited local skin alterations, while some also presented with systemic symptoms. Univariate analysis showed GM was relevant to gestation history, menopause, nipple discharge and invagination, high prolactin level, sex hormone intake, thyroid function, SDS score, breast trauma and diet preference (P < 0.05). Multivariate logistic analysis showed ages (20-40 years old), high prolactin level, sex hormone intake, breast trauma, nipple discharge or invagination and high SDS score were independent risk factors for GM. The mean area under the curve (AUC) in the modeling group was 0.899, and the AUC in the validation group was 0.889. The internal and external validation demonstrated the model's predictive ability and clinical value. Conclusion: The lactation-related factors are the main risk factors of GM, which could lead to milk siltation or ductal secretion increasing. Meanwhile, hormone disorders could affect the secretion and the expansion of mammary ducts. They all can obstruct or injure the duct, inducing inflammatory reactions and immune responses. Blunt trauma, depressed mood and diet preference can accelerate the process. The Nomogram can effectively predict the risk of GM's occurrence.