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.