POS0621 GRANULOMATOUS MASTITIS: EXPERIENCE WITH DIAGNOSIS AND MANAGEMENT

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Background: Idiopathic Granulomatous Mastitis (IGM) is a chronic benign inflammatory breast disease. Although etiology is still not clear, multiple risk factors have been proposed and its currently thought to be a local autoimmune reaction triggered by a bacterial infection. Recent literature indicates a relation between Corynebacterium, especially the kroppenstedtii species. It presents with a firm, painful unilateral breast mass (occasionally bilateral), swelling, fluid collections and skin changes that can include erythema, ulceration and fistula, mimicking an acute mastitis or cancer. Patients are most commonly young childbearing age women. Diagnosis is made by histopathologic examination (core biopsy or surgical excision). Pathologic features show non-caseating granulomas surrounded by polymorphonuclear cells and multiple giant cells located at the center of breast lobules. There aren´t unified guidelines for diagnosis and treatment. Multidisciplinary team management strategies should be considered. Objectives: The purpose of this study is to describe the clinical, bacteriological and pathological characteristics and the therapeutic approach of patients diagnosed with IGM at a public hospital in Buenos Aires. Methods: This prospective, descriptive, observational study of patients with IGM was performed between 2017-2024. Demographic data were colleted, pregnancies, breastfeeding and breast history, clinical presentations according to the four Yaghan IGM patterns [1] (A: asymptomatic tumor, B: inflammatory tumor, C: tumor with abscess, D: tumor with fistula and/or ulcer, adding "e" when associated extramammary disease was present). Breast imaging, cultures, PPD test, and chest X ray were evaluated. Tissue pathological examination include hematoxylin and eosin staining and additional Ziehl-Neelsen, PAS, Gram and Giemsa stains were performed. Treatments, evolutions, complications, sequelae, and recurrences were analyzed. Cure was defined as clinical and imaging signs absence once treatment was accomplished, and recurrence as its appearance after 3 months from healing. Results: A total of 100 patients were analyzed. Demographic characteristics (Table 1). The clinical presentations were pattern C 43%, B 33%, A and D 12% and e 9%. Ultrasound (US) was performed in 100%, mammography in 74% and magnetic resonance imaging in 11%. US most frequent findings were hypoechoic irregular Doppler+ mass with collections, subcutaneous sinus and tracks. Biopsy was performed in all patients and the findings revealed Granulomatous Mastitis (MG) in 58% and Cystic Neutrophilic Granulomatous Mastitis (CNGM) in 42% [2, 3]. Cultures samples were performed in 92% of the cases. Corynebacterium was detected in 59% of the samples by culture and/or histology. Treatment strategies included antibiotics in 84%, associated Corticosteroids in 73% and Methotrexate in 51%. Abscess drainage or tumorectomy were performed in 25%. Recurrences were seen in 14%. Conclusion: The strong association with Corynebacterium in our population is a current topic of research. The importance of concomitant treatment with immunosuppressants plus antibiotics is highlighted, reinforcing the role of reactive autoimmunity in its etiopathogenesis. REFERENCES: [1] R. Yaghan, Hamouri S., Ayoub N., Yaghan L., Mazahreh T. A proposal of a clinically based classification for idiopathic granulomatous mastitis. Asian Pacific Journal of Cancer Prevention, 2019; 2. [2] Taylor G., Paviour S., Musaad S., Jones W. and Holland D. A clinicopathological review of 34 cases of inflammatory breast disease showing an association between corynebacteria infection and granulomatous mastitis. Pathology 2003; 35: 109-119. [3] Renshaw A., Derhagopian R., and Gould E. Cystic Neutrophilic Granulomatous Mastitis: An underappreciated pattern strongly associated with gram positive bacilli. Am J Clin Pathol 2011; 136: 424- 4270:929-934. Table 1Demographic characteristics.Age yrs old (median)40 (19-66)Menarche (age)13,46Pregnancies (nº pregnancies: n patients)0: 101: 262: 233 or >: 41Lactation (n)87Duration of lactation (months)10-60Time between lactation and MG (months)76,56Obesity Class I and II (n)7 y 5Smoking (n)4Time between MG and consultation (months) (median)2 (1-12) Acknowledgements: NIL . Disclosure of Interests: None declared . © The Authors 2025. This abstract is an open access article published in Annals of Rheumatic Diseases under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Neither EULAR nor the publisher make any representation as to the accuracy of the content. The authors are solely responsible for the content in their abstract including accuracy of the facts, statements, results, conclusion, citing resources etc.

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