Accessory breast tissue is extra breast gland or skin that didn’t disappear during normal development. It usually sits along the “milk line” from the armpit to the groin, most often under the arm or near the bra edge. The signs are straightforward. Many people notice a soft, puffy swell under the arm that enlarges during periods or pregnancy. It can feel like a small rubbery pad, sometimes with a tiny nipple or darkened skin in the center. Hormonal swings often make it tender, achy, or itchy—much like normal breasts. Some feel burning or pulling if the tissue swells quickly. If... Learn more