A BI-RADS (Breast Imaging Reporting and Data System) 3, or probably benign, assessment is given in approximately 7% to 12% of breast magnetic resonance (MR) images. However, the imaging features of probably benign lesions on MR imaging have not been well defined. As with mammography and ultrasonography, a BI-RADS 3 assessment should be used only when there is a less than 2% likelihood of malignancy. The use of BI-RADS 3 for classically benign findings should be avoided. Certain masses, foci, and areas of nonmass enhancement may be categorized as probably benign on baseline MR imaging.
