Most calcifications in the breast form either

–     Within the terminal ducts (intraductal calcifications A; BI-RADS 4-5), or  

–     Within the acini (lobular calcifications B; benign)

(Smithuis 2008)

diagram of TDLU and calcs, modified from Images: Smithuis 2008

Most important descriptors for calcifications are

–     Morphology  

–     Distribution

Distribution and morphology need to be assessed together, ex: if the morphology is possibly concerning (amorphous), but the distribution is very reassuring (diffuse and bilateral) = benign

(Ikeda 2010)