Ricerc@Sapienza

The presence of ectopic or supernumerary breast tissue is a rare event, related to a not complete regression of breast tissue along the milk line. Primary ectopic breast cancer of the axilla can create many difficulties in differential diagnosis with subsequent delayed specific treatments. The incidence of ectopic breast tissue is 0.2-6%, and the axilla is the most common site involved. In this tissue, the same physiologic and pathologic changes as seen in ectopic breast tissue may occur, including carcinoma formation.