Background: Idiopathic granulomatous mastitis (IGM) is a benign breast disease that has been described as a rare granulomatous inflammation (GI). It can mimic inflammatory breast cancer., Material and Methods: We included women with a diagnosis of IGM referred to an oncologic hospital between January 01, 2007 and to March 31, 2011, with diagnosis of breast cancer, in whom biopsy reported GI, without other cause related. The aim of this study was to review the clinical, radiologic and pathologic characteristics of a cohort of women with IGM., Results: We analyzed 58 patients; mean age was 38 ± 12 years. Mammography showed diffuse asymmetry (n = 19) and focal asymmetry (n = 13); breast ultrasound showed heterogeneous and hypoechoic areas (n = 28) and lumps (n = 21) as the most frequent lesions. All biopsies showed lobulocentric GI. Treatment included antibiotics (n = 20), steroids (n = 8), both treatments (n = 20), surgical excision (n = 3) and observation (n = 7). Forty-three patients (74%) had complete remission; mean time to remission was 9.5 ± 5.8 months. Fifteen (26%) had partial remission. Any patient had progression or relapse., Conclusions: IGM is a benign breast condition that may mimic breast inflammatory cancer. Ultrasonography and mammography findings reveal characteristic data that can be useful for establishing the diagnosis; however, biopsy is the gold standard for its diagnosis and should be taken in any patient even with a mild suspicion of cancer.