If you're concerned by axillary breast tissue in your armpit or otherwise, you're not alone. According to a 2024 study in the Journal of Family Medicine and Primary Care, up to 6 percent of women (and 3 percent of men) have breast tissue located outside of the typical area.
Because this breast tissue is made up of some fatty elements, it's possible that exercise and fat loss could affect the appearance of excess tissue, but it is not the primary treatment; surgical excision and liposuction are the most effective methods of removing axillary breast tissue.
Here’s everything you need to know about exercise’s impact on axillary breast tissue.
What Is Axillary Breast Tissue?
According to the Journal of Family Medicine and Primary Care study cited above, axillary breast tissue – also known as accessory breast tissue or ectopic breast tissue – is extra breast tissue on the body where it normally wouldn't be. It is very often around your armpit.
This tissue growth happens when you are still developing in the womb, and some of the cells that could turn into breast tissue don't completely disappear from other areas of the body.
Axillary breast tissue is most frequently located along the mammary ridge, or “milk line,” which is a path from your armpit to your groin. However, a guide on accessory breast tissue by the American Journal of Roentgenology states this type of tissue can also be located on the face, back of the neck, mid-back, buttocks, vulva, hip, shoulder, and thigh.
The American Academy of Family Physicians explains that axillary breast tissue is a normal occurrence, not an abnormality. It is most often removed in cases where it causes discomfort, or for aesthetic reasons.
What It’s Not: Underarm Fat
Axillary breast tissue is not the same thing as excess underarm fat. If you have not received a medical diagnosis, what you think is axillary breast tissue may just be excess body fat that has collected in your underarm area. It's best to consult your doctor so you know exactly what you’re experiencing.
Axillary breast tissue in the armpit isn't any different than other breast tissue; it’s composed of fibrous and fatty tissues. When you lose a lot of weight, your breast size may decrease because you lose some volume in your breasts. That means your axillary breast tissue may also appear to decrease in size — but it will not disappear, just as your breasts will not disappear with weight loss.
When Exercise Can Help (and Tips)
If it is just excess body fat, eating less and exercising more can make a significant difference.
But what kind of exercise is best and how much should you do? The Physical Activity Guidelines for Americans from the U.S. Department of Health & Human Services are a good place to start.
According to these guidelines, adults should get at least 150 to 300 minutes of moderate-intensity, or 75 to 150 minutes of vigorous-intensity, aerobic exercise each week. Examples of moderate-intensity exercise include brisk walking, dancing, gardening, biking at a place slower than 10mph, playing doubles tennis and doing water aerobics.
Vigorous activities include running, hiking uphill, swimming laps, aerobics classes, heavy yard work, singles tennis, jumping rope and cycling at a speed of more that 10mph, according to these guidelines. If you haven't previously done any exercise, take it slow and gradually increase the time you spend being active.
The U.S. Department of Health & Human Services also recommends that adults do some type of resistance training for the entire body at least two days a week. This could mean going to the gym and lifting weights, doing body-weight exercises at home or taking a class such as Pilates or yoga.
Focus on the whole body when weightlifting — not just the area around the breast tissue. Building muscle mass helps burn fat because muscle is more metabolically active than fat. The more muscle you have, the more calories your body will burn even while you are at rest, explains the Mayo Clinic.
Keep in mind that if you do see changes from fat loss from exercise, it may not be exactly where you wanted to see them. When you lose total body fat, it comes from all over your body, and it might come from your face, thighs, and stomach before it affects your breasts and underarm breast tissue. And, although targeted chest exercises can help to firm your pectoral muscles, they will not affect the appearance of underarm breast tissue.
Removing Auxiliary Breast Tissue
The only proven ways to get rid of axillary breast fat, according to the American Journal of Roentgenology article, are surgical excision and liposuction.
Excision is the treatment of choice when excess tissue causes discomfort, because a larger volume of tissue can be removed. When removal is for aesthetic purposes, liposuction may be all that's necessary. In some cases, excision and liposuction will be used together.
Talk to Your Doctor
Axillary breast tissue is subject to the same conditions and diseases as normal breast tissue, which is another reason that it’s important to see your doctor to determine whether your underarm tissue is breast tissue or simply fat. These could be benign cysts or tumors, or they could be malignancies such as ductal cancer, according to the Journal of Family Medicine and Primary Care.
