Corynebacterium in Granulomatous Mastitis: Clinical Features and Treatment Outcomes

Objective: Granulomatous mastitis (GM) is a chronic inflammatory breast disease with a heterogeneous clinical presentation and uncertain optimal management. Increasing evidence suggests a role for Corynebacterium species, particularly Corynebacterium kroppenstedtii, in its pathogenesis. This study aimed to evaluate the clinical characteristics, treatment strategies, and outcomes of granulomatous mastitis, with particular emphasis on cases associated with Corynebacterium species and the impact of antibiotic therapy. Materials and Methods: This retrospective cohort study included female patients with GM treated at a university hospital between January 2018 and January 2023. Patients were grouped according to Corynebacterium isolation. Clinical characteristics, microbiological findings, and treatment modalities-oral steroids, combined antibiotic-steroid therapy, antibiotics with intralesional steroids, and segmental mastectomy-were evaluated. The impact of lipophilic antibiotics (tetracyclines, linezolid, rifampin) combined with steroids was assessed. Recurrence rates and associated factors, including symptom duration, were analyzed. Results: A total of 165 patients were included in the study, of whom 25 tested positive and 140 negative. Corynebacterium spp. were detected in 15.15% of cases, with C. kroppenstedtii identified in 8.48%. Patients with Corynebacterium-associated GM had more extensive abscess formation and required more interventional procedures. Multimodal treatment strategies combining steroids, antibiotics, and surgery resulted in favorable outcomes. Lipophilic antibiotics combined with steroids showed a positive but statistically non-significant effect. Recurrence occurred in 16.4% of patients and was associated with longer symptom duration. Conclusion: Accurate microbiological identification is essential in GM, particularly in C. kroppenstedtii infections, to guide targeted antibiotic therapy and reduce recurrence. Tailored management strategies, including lipophilic antibiotics, may improve outcomes. Further studies are needed to define optimal treatment duration and the role of surgery in refrac-GM.