How does accessory breast tissue form? Where is it most commonly located?
Breast tissue development begins at about 6 weeks of gestation and originates from ectodermal elements. The “milk line” extends from the groin region to the axillary region. Most of the potential breast tissue atrophies except in the fourth intercostal region, where “normal” mammary tissue eventually develops. The lack of appropriate regression results in accessory breasts anywhere along the “milk line.”