Idiopathic Granulomatous Mastitis: A Rare Disorder to Consider in the Differential Diagnosis of a Breast Mass

Idiopathic granulomatous mastitis (IGM) is a rare inflammatory breast condition that resembles infectious mastitis and malignancy, making diagnosis and treatment challenging. We report the case of a 32-year-old woman with a painful, enlarging left breast mass. Ultrasound-guided biopsy demonstrated cystic neutrophilic granulomatous mastitis. Her infectious work-up yielded negative results. The patient was treated with antibiotics that were then discontinued after biopsy and negative culture and she was discharged on steroid taper. Over the subsequent 18 months, she had steroid-dependent flares and, despite methotrexate and adalimumab, required a lumpectomy. This case highlights the need for early recognition of IGM in breast masses and the challenges in diagnosis, management, and care.