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I recently noticed a small lump in my armpit. Could this be a sign of breast cancer

“It could indeed be a sign of breast cancer,” says Allison Hatmaker, MD, of Baptist Surgical Associates, who is board certified in general surgery and fellowship trained in breast surgery.

First, breast tissue sometimes extends up into the armpit region. A lump felt in your underarm could in reality be a lump in your breast; you just never realized your breast extended that far. Second, the lymph nodes in your armpit filter out any abnormalities (infections, reactions to drugs, cancer) in the same-side chest wall, arm or breast.

“A lump under your arm may indicate that your lymph nodes have identified, and are trying to fight, cancer cells that have reached them from your breast,” Dr. Hatmaker explains.

You should see the doctor if the lump doesn’t disappear on its own within a couple of weeks; or if it appears to be getting worse. There are many causes of underarm lumps, and the vast majority have nothing to do with cancer.

The most prevalent cause of a lump in the armpit is infection. An infection can be localized to the
armpit itself (perhaps a nick from shaving); or it can be more widespread. It’s possible to get a localized infection from using an antiperspirant rather than a deodorant; antiperspirants prevent your sweat glands from releasing germs that can cause infections. Or you may have a boil or abscess just under the skin.

Viral infections, such as shingles, chickenpox and infectious mononucleosis often cause underarm
lumps. You may also get a lump under your arm as a reaction to a vaccination, such as smallpox, typhoid or, rarely, measles/mumps/rubella. Sometimes, an allergic reaction to penicillin or iodine produces an underarm lump.

A lump that’s moveable and painful signifies an infection. And, while a painless lump that’s hard and fixed in place is more likely to be cancer than one that’s painful, softer, and moveable, such a lump doesn’t automatically signify cancer. In fact, an unexplained lump has about a 4 percent chance of being malignant, if you’re over the age of 40; and about a .4 percent chance of malignancy if you’re under 40.

“In addition, a lump that seems to increase in size within a few days is probably due to infection, rather than malignancy. Redness/soreness of the skin is also often a sign of a lymph node infection, not cancer,” Dr. Hatmaker adds.

Need a physician or specialist? The Baptist Hospital East Physician Referral Service can help you find a physician near you who participates in your insurance plan. Call (502) 897-8131, or search the Physician Directory.

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