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 the area stays warm and red, it may have an infection or abscess, which needs antibiotics or drainage.

Rarely, the extra tissue leaks a few drops of milk after childbirth. If a firm lump that doesn’t shrink after the cycle appears, or if the skin dimples or ulcers, see a doctor to rule out breast cancer in the accessory gland. Otherwise, simple observation or easy outpatient removal solves the problem.

Symptom	What It Feels or Looks Like
Soft puffy swell under arm/bra line	Grows with periods or pregnancy
Small rubbery pad or nipple-like bump	May darken or leak milk postpartum
Tenderness, ache, itch, burning	Worsens during hormonal peaks
Warm red skin	Possible infection or abscess
New hard lump, dimple, ulcer	Needs check for cancer