This document outlines the BI-RADS categories for mammography. It describes breast composition, mass characteristics including shape and margins, and other findings like asymmetries, architectural distortion, and calcifications. Breast composition ranges from almost entirely fatty to extremely dense. Mass shape can be oval, round, or irregular, and margins can be circumscribed, obscured, microlobulated, indistinct, or spiculated. The BI-RADS categories are also defined, ranging from 0 (needs more imaging) to 5 (highly suggestive of malignancy) to 6 (known biopsy).