Features of non-mass enhancing lesions detected on 1.5 T breast MRI: A radiologic and pathologic analysis

Background With increased utilization of magnetic resonance imaging (MRI) of the breast in clinical practice, many non-mass lesions are being detected incidentally. Although MRI-guided biopsies are usually performed for these lesions, no clear guidelines exist to determine the management of these lesions. Objective The purpose of this study was to explore the pathological features of incidentally detected non-mass lesions on breast MRI to determine rates of malignancy and to assess the predictive value of kinetic enhancement curves for further characterization of these lesions as benign versus malignant. Methods A retrospective review was performed of all MRI-guided core needle biopsies done at our institution between January 2009 and January 2012. Results 172 consecutively biopsied lesions were identified. 43% of the lesions were non-mass lesions, out of which 74.3% were benign, whereas 14.9% and 10.8% of these lesions had malignant and atypical features, respectively. The most commonly encountered non-mass malignant lesion was ductal carcinoma in situ, whereas the most frequently seen invasive non-mass lesion was invasive lobular carcinoma. Kinetic enhancement curves for these lesions did not demonstrate a statistically significant relationship with their pathologic features. Conclusions Non-mass enhancing lesions incidentally detected on breast MRI carry a significant risk of atypia and malignancy, either in situ or invasive. Hence, it is prudent to biopsy these lesions.