Idiopathic granulomatous mastitis (IGM) is a rare localized granulomatosis of unknown aetiology that usually affects women of childbearing age. It often mimics breast carcinoma or abscess. Histopathologic evaluation and elimination of the others aetiologies of granuloma play a crucial role in the diagnosis. Its etiopathogeny remains poorly understood, but Corynebacteria might be involved. The disease course is usually protracted, with a significant impact on quality of life. The management of IGM remains controversial, but corticosteroids are usually the first-line treatment.