This chapter deals with practical problems in the handling and reporting of breast core biopsy specimens, including approaches for identification of histological microcalcifications. The use of reporting categories (“B” codes) is recommended, and the chapter largely concentrates on those entities causing diagnostic difficulties, such as the B3 lesions, of uncertain malignant potential, as well as potentially problematic malignant lesions, albeit these make up a minority of a pathologist’s routine practice.