Ectopic breasts: familial functional axillary breasts and breast cancer arising in an axillary breast.

Supernumerary breasts and nipples are not uncommon and have familial and syndrome associations. Although usually of only cosmetic concern, hormonal changes and inflammatory or neoplastic conditions that affect primary breast tissue also may occur in areas of ectopic breast tissue. We describe cases of familial functional axillary breasts and primary carcinoma of the breast arising in ectopic axillary breast tissue.