Magnetic Resonance Imaging Features of Idiopathic Granulomatous Mastitis: A Retrospective Analysis

BACKGROUND: Granulomatous mastitis is a rare and benign inflammatory breast disease that may clinically and radiologically mimic breast cancer. OBJECTIVES: The aim of this study was to evaluate the features of idiopathic granulomatous mastitis (IGM) on breast magnetic resonance imaging (MRI) with mammographic and sonographic findings. PATIENTS AND METHODS: A retrospective analysis was conducted on 20 patients with IGM who had been diagnosed by needle core or excisional biopsy at a single institution between 2006 and 2012. All of the patients underwent MRI for suspicious breast findings prior to biopsy. MRI examinations were performed on a 1.5 T scanner. The MRI findings were evaluated in accordance with the breast imaging-reporting and data system (BI-RADS) MRI lexicon established by the American College of Radiology. RESULTS: MRI detected a total of 29 lesions in the 20 patients. Fourteen of these lesions were seen as mass enhancements, with the remaining 15 identified as non-mass enhancements (NMEs). The median size of all lesions was 3.6 cm (range, 0.7 - 6.7 cm). The most frequently observed features were masses with a round shape (9 out of 14, 64%), smooth contour (11 out of 14, 78%), and a rim enhancement pattern (10 out of 14, 71%). The most common features of the 15 NME lesions were segmental distribution (6 out of 15, 40%) and heterogeneous enhancement patterns (8 out of 15, 53%). The time-intensity curves of the dynamic studies showed benign type one signal intensity (persistent enhancement pattern) in the majority of lesions (10 out of 20, 50%). CONCLUSION: Our study suggests that breast MRI findings of IGM have a wide spectrum. Rim enhancement patterns are frequently seen on contrast enhanced images, but the imaging findings are nonspecific and cannot be used definitively to distinguish between benign and malignant lesions.