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... Learn more