BENIGN tumefactions of breast tissue and its integument may be divided into: A. Mammary dysplasia, resulting from abnormalities in the secretion of the ovarian hormones. This is exemplified by: (1) Mastodynia—painful mammary tissue of increased density. (2) Adenosis—nodosities from epithelial hyperplasia with small cysts. (3) Cystic disease—one or more cysts of appreciable size resulting from secretory changes. B. Benign neoplasia, characterized by true benign tumor formations. Examples of this are: (1) Benign fibroadenoma with a structure of fibrous tissue and ducts. (2) Benign intracystic papillomas, which include (1) papillary invaginations of larger ducts, (2) intracystic papillomas and (3) papillary hyperplasia which occurs in adenosis of the breast. (3) Benign nonindigenous tumors of the breast, involving (a) fat (lipoma and xanthoma), (b) lymphatic vessels (angioma, lymphangioma and lymphoma), (c) muscles (leiomyoma and myoblastoma), (d) skeletal mesenchyme (chondroma and osteoma) and (e) skin