Supernumerary nipple and breast malformations are extra breast parts that develop along the “milk line” before birth. They can show up anywhere from the armpit to the groin and range from tiny moles to full extra breasts.

The commonest form is a single spare nipple—often a small, pink- or brown-tinted bump under the normal breast or in the armpit. It may look like a freckle and is easy to miss until hormone changes make it swell or tingle during periods, pregnancy, or breast-feeding. Some people have a complete extra breast with gland tissue, areola, and even a nipple that enlarges and feels tender much like the main breasts.

Extra tissue can ache or itch when hormones surge, and clothing rubbing can cause redness or a rash. If the area becomes warm, hard, and painful, an infection or abscess has set in and needs antibiotics. Rarely, the extra gland develops a firm lump that doesn’t shrink after the menstrual cycle; any new, growing, or irregular mass should be checked to rule out breast cancer in the supernumerary tissue.

Most extra nipples or breasts are harmless and can be left alone, but they are easily removed under local anesthetic if they hurt, look unsightly, or worry you.