by Zaid Haddadin,MD, and Jane Dascalos, MD
According to the ACR BI-RADS (Breast Imaging-Reporting and Data System) atlas a breast mass is three-dimensional and occupies space. It is seen in two different mammographic projections. It has completely or partially convex (having an outline or surface curved like the exterior of a circle or sphere) outward borders and (when radiodense) appears denser in the center than at the periphery. If a potential mass is seen only on a single projection, it is called an asymmetry until its 3-dimensionality is confirmed. A breast mass is characterized using BI-RADS lexicon in the following three categories: 1) Shape 2) Margins 3) Density
The margin is the edge or border of the lesion and is an important predictor of whether a mass is benign or malignant
Density is used to define the x-ray attenuation of the mass relative to the expected attenuation of an equal volume of normal fibroglandular breast tissue.