What are the ACR recommended morphologic descriptors for abnormal enhancement on breast MRI?
The ACR has developed a Breast Imaging-Reporting and Data System (BI-RADS) Atlas for mammography, US, and MRI reporting. According to the Atlas, each lesion should be characterized based on size, location (breast quadrant), and affected breast (right or left). Additional morphologic descriptors depend on whether the lesion is discrete with convex borders (mass) or not discrete with concave or unclear borders (nonmass). A mass is additionally characterized according to shape (oval, round, irregular), margin (circumscribed, irregular, spiculated), and internal enhancement (homogeneous, heterogeneous, rim, dark internal septations). Nonmass enhancement is usually described according to the distribution (focal, linear, segmental, regional, multiple regions, diffuse) and internal enhancement pattern (homogeneous, heterogeneous, clumped, clustered ring). If a lesion is too small to be characterized (≤4 mm) and the radiologist would like to call attention to it, it can be called a focus.