Idiopathic Granulomatous Mastitis of the Breast: Radiologic-Pathologic Correlation

Granulomatous inflammation is an uncommon inflammatory condition of the breast that includes both infectious (bacterial, fungal, parasitic) and noninfectious (autoimmune, sarcoidosis, idiopathic granulomatous mastitis [IGM], reaction to foreign materials) etiologies. IGM is the most common subset of granulomatous inflammation where no underlying etiology is established. Infectious causes of granulomatous inflammation should be excluded, as these have established treatments that can significantly improve patient outcomes. IGM should be considered in the differential when mastitis is refractory to antibiotics. Patients usually present with an erythematous, tender, palpable unilateral breast mass. The most common mammographic presentation is a focal or global asymmetry. The imaging appearance mimics breast cancer, therefore diagnosis usually requires tissue sampling with histopathologic analysis and cultures to exclude infection. When patients are diagnosed with IGM, this poses a clinical dilemma as there are a variety of treatment options available, including oral and intralesional steroids. The time course of the disease is often prolonged by multiple recurrences, and specific treatment remains an area of ongoing research. The purpose of this article is to review the range of clinical features, imaging manifestations, associated histopathology, and management of IGM.