Accessory nipples

In utero, the breasts develop from the mammary ridge (milk line), an ectodermal thickening that initially extends from the axilla to the medial thigh bilaterally.

The remainder of the mammary ridge subsequently regresses in early gestation.

Incomplete involution of the mammary ridge results in an accessory nipple (sometimes with associated glandular tissue) anywhere along this ridge.

The most common location of an accessory nipple is inferior to the breast.

Accessory nipples are usually asymptomatic, well-circumscribed, hyperpigmented papules.

They may become larger during puberty, before menses, or with pregnancy/lactation due to rising estrogen and progesterone (similar to physiologic changes in normal breast tissue).

Associated glandular tissue may also become tender or swollen.

The diagnosis is clinical, and no treatment is generally required.