Breast imaging reporting and data system category 3 for magnetic resonance imaging

The Breast Imaging Reporting and Data System (BI-RADS) category 3 signifies a probably benign finding and should be reserved for those findings that have a less than 2% risk of malignancy. There are limited data defining the use of this category in magnetic resonance imaging (MRI) and the imaging features of probably benign lesions are not well defined. Most recent studies have shown that the frequency of use of BI-RADS 3 is comparable with that reported in mammography and ultrasound and that the rate of malignancy is within the targeted range. Several findings, once assessed as BI-RADS 3, are nowknown to represent benign entities, such as variations of background parenchymal enhancement and intramammary lymph nodes. A subset of masses, foci, and nonmass enhancement can appropriately be assigned BI-RADS 3 on baseline MRI. The BI-RADS 3 is most appropriately used for round, dotlike foci, which are unique and separate from background parenchymal enhancement and for oval masses with circumscribed margins and homogeneous enhancement, such as those typically seen in incidental fibroadenomas. The BI-RADS 3 may also be appropriate for a focal or regional distribution of nonmass enhancement without suspicious features.