Epidemiological, Clinical, and Therapeutic Characteristics of Idiopathic Granulomatous Mastitis Treated With Ultrasound-Guided Intralesional Steroid Injection

Background: Idiopathic granulomatous mastitis is a rare benign chronic inflammatory breast disease with heterogeneous clinical and radiologic presentations and no standardized treatment. This study aimed to describe the epidemiological, clinical, radiologic, and therapeutic characteristics of patients with biopsy-proven idiopathic granulomatous mastitis treated with ultrasound-guided intralesional steroid injection. Methods: We conducted a retrospective observational study at a breast department in Salvador, Brazil. Medical records from May 2023 to January 2024 were reviewed. Patients with histologically confirmed granulomatous mastitis, negative bacterial and fungal cultures, and treatment with ultrasound-guided intralesional triamcinolone acetonide were included. Clinical, radiologic, treatment, and response data were analyzed descriptively. Results: Ten females were included. The mean age was 35.8 years, and all patients were premenopausal. Pain or tenderness with hyperemia was observed in nine patients (90%). All patients had skin involvement, and three (30%) had fistulas. The mean number of intralesional steroid injections was 3.3, and the mean follow-up was 5.7 months. Complete clinical response occurred in five patients (50%), partial response in three (30%), and no response in two (20%). Complete radiologic response occurred in four patients (40%). No patient required surgery. One patient developed skin retraction. Conclusions: Ultrasound-guided intralesional triamcinolone injection appears to be a feasible conservative treatment option for idiopathic granulomatous mastitis, with clinical or radiologic response in most patients and limited adverse events. Larger prospective studies are needed to define optimal dosing, durability of response, recurrence rates, and long-term safety.