What To Know About Accessory Breast Tissue

Accessory breast tissue is more common than many people realize. While having extra breast tissue is usually harmless, for some it can cause discomfort or self-consciousness and when that happens, help is available.

Constanze Rayhrer, MD, a board-certified surgeon specializing in breast surgery with Franciscan Health Lafayette East, explains what accessory breast tissue is, why it occurs, and when to consider treatment.

Key Takeaways: Accessory Breast Tissue

• Accessory breast tissue is a common, normal anatomical variation, affecting about 5% of women (and some men), and can develop anywhere along the milk line—from the armpit to the groin.
• Hormonal changes often make this tissue noticeable, especially during puberty or pregnancy, when swelling or lumps may appear under the arm.
• Accessory breast tissue can respond to hormones and carries the same cancer risk as regular breast tissue, meaning it should be monitored and evaluated like typical breast tissue.
• Treatment is only recommended if the tissue causes discomfort or emotional distress, and removal is a simple outpatient procedure that can provide significant relief.

What Is Accessory Breast Tissue?

Accessory breast tissue is a variation in anatomy that some people are born with. Dr. Rayhrer explains that "about 5% of women have it — so one out of 20."

During early development, the milk line, running from the armpits down to the groin is completely normal, and breast tissue can form anywhere along that line.

"Usually, that tissue regresses before we're born," she said. "But in about 5% of women and some men, we can have extra areas of breast tissue anywhere along that line."

Most people don't realize they have accessory breast tissue until hormonal changes occur, typically during puberty or pregnancy.

Where Is Accessory Breast Tissue Found?

Accessory breast tissue can form anywhere along the milk line, from the armpit to the groin. The most common location is under the arms, where swelling or lumps may appear as hormones stimulate the extra tissue.

Accessary breast tissue can also vary in appearance.

"We can see nipples without breast mounds, breast tissue mounds without nipples, or both together," Dr. Rayhrer explained.

One of the most common presentations is extra nipples, which are often mistaken for freckles because they're small and flat.

When Do Patients Typically Notice Accessory Breast Tissue?

In most cases, people don't recognize accessory breast tissue on their own. Sometimes it's identified by a family member who's familiar with it because they have had it before.

"Typically, men think it's a freckle," Dr. Rayhrer said. "The most common presentation in men is an extra nipple, and it can be very subtle."

For women, the extra breast tissue often becomes noticeable during puberty or pregnancy, when hormones cause swelling in the area under the arm.

"It can be confused with other conditions that are more worrisome," she added, "and they go to a doctor and find out it's accessory breast tissue."

For some women, the bulge can be uncomfortable or even embarrassing.

"It can really feel like there's a lump under the arm, like you're carrying a ball under your arm," Dr. Rayhrer said.

Does Accessory Breast Tissue Cause Discomfort?

It depends on the size and amount of tissue. Smaller areas usually don't cause issues, but larger ones can.

"If it's very small, people are just reassured to know that it's a normal variant," said Dr. Rayhrer. "If it's larger, it can be really uncomfortable and interfere with wearing some clothing."

Can Accessory Breast Tissue Respond To Hormones Or Lactation?

Yes. Accessory breast tissue contains glandular cells that respond to hormonal changes just like normal breast tissue.

"Breast glandular tissue without a nipple can swell up during pregnancy and be uncomfortable," Dr. Rayhrer said. "Occasionally, women will notice milk production from what they thought was a freckle, typically under the arm."

After breastfeeding, the tissue may shrink, but sometimes it remains enlarged. "It can stay quite large, and people would like to have it removed," she added.

Does Accessory Breast Tissue Carry A Risk Of Breast Cancer?

"So yes, it does carry a risk of breast cancer similar to normal tissue," Dr. Rayhrer said.

Because accessory breast tissue is composed of the same types of cells as regular breast tissue, it can develop the same conditions, including cancer.

Fortunately, for women, the most common area for accessory tissue is under the arm and that is typically included in routine mammograms.

"If there is tissue outside of that area, we should check on it too," she said.

When Is Treatment Or Removal Recommended?

"Whether we remove the tissue or not really depends on how much it's interfering with someone's life," said Dr. Rayhrer.

For some, simply understanding that it's a normal variant is enough reassurance, and they can keep living their normal lives. For others, especially if the area is painful, noticeable, or emotionally distressing, surgery can be an option.

"It is a short outpatient surgery to remove the tissue," she explained. "It's not difficult, and it can be quite a relief, especially if someone has been teased or if it's been very uncomfortable."

What's The Most Important Advice For Someone Who Finds A Lump Along The Milk Line?

"The first thing we always want to do is make sure a lump is not something more important than accessory breast tissue," Dr. Rayhrer said. "It's always good to check in with your doctor, check in with a breast specialist, get your imaging."

If a person has accessory breast tissue, it simply needs to be monitored like any other breast tissue.

"There's nothing wrong with a person that has accessory breast tissue," she said. "It's completely normal, just one of those things that make each one of us unique."