Tumors of fatty tissue in the breast, including lipoma, fat necrosis, and xanthoma, although unusual, arc ncvcrtheless important and should be recognized. Thc scarcity of discusRions in the literature on this subject can be attributed to the relatively infrequent occurrence of these lesions. Of approximately 3,000 breast tumors collected in this laboratory, only 58 cases could be classified as fatty tissue tumors (Table I).