Breast lipomas are benign breast lesions and are classified as BIRADS II lesions. On mammography typically seen as a radiolucent mass with homogeneous fat density and sometimes with minimal soft tissue density. Enlargement of a lipoma is an indication for biopsy, although they rarely undergo malignant transformation and are not associated with an increased risk of developing breast cancer.

Breast hamartoma can be considered in a differential list but usually shows more heterogeneous appearance with scattered areas of soft tissue density, causing a "breast within a breast"  or a "slice of sausage" appearance. Breast hamartomas are also classified as BIRADS II lesions.