Should I Be Concerned About a Lump in My Armpit?

  • A lump under the armpit is usually an enlarged lymph node.
  • An enlarged lymph node with certain characteristics can be a sign of cancer in rare cases.
  • Regardless of the lump’s characteristics or accompanying symptoms, it is reasonable and likely a good idea to have it checked out by a doctor if it does not resolve on its own.

It can be alarming to discover an unusual lump in your armpit, but most of the time, a lump under the armpit is nothing to be concerned about.

Adrienne Waks, MD, a physician at Dana-Farber’s Susan F. Smith Center for Women’s Cancers, answers some of the most frequently asked questions about a lump under the armpit, including when to seek medical attention.

What is the meaning of a lump under the armpit?

Lymph nodes are a vital part of the immune system, and they can swell when the body is fighting an infection or recovering from an injury. A lump under the armpit is usually an enlarged lymph node.

The lump could be an enlarged lymph node if the skin appears normal but there is a bump under the skin.

If the lump disappears, the lymph node was most likely swollen as a result of an infection or inflammation. It’s common practice to keep an eye on the lump for a few days to see what happens. Symptoms of infection, such as redness, pain, or fever, can accompany a swollen lymph node and should be checked out by a doctor.

Something in the skin, such as a cyst or a blocked hair follicle, is another common cause of a lump under the armpit.

An enlarged lymph node with certain characteristics can be a sign of cancer in rare cases.

What does it feel like to have a cancerous lump in your armpit?

It will also lose its lima bean shape and take on a more marble-like shape. It should be firm but still have some give to it. A cancerous lymph node can become extremely hard. A healthy lymph node should resemble a lima bean.

Similarly, if the lump is clearly not in the skin and persists, grows larger, and isn’t accompanied by signs of infection, it’s time to seek medical help. It’s possible that a swollen lymph node is cancerous if it’s overly firm and not shaped like a lima bean.

Remember that cancer cannot be diagnosed by touch, so if you are concerned or notice these symptoms, you should see your doctor. While a lump in the armpit is usually nothing to be concerned about, and the cause is usually something minor and innocuous, it is better to be safe and have it checked out.

Is it possible that a painful lump in the armpit is cancer?

If a lump in the armpit is painless, it is more concerning. Pain and tenderness are more common in infections and inflammation, whereas cancer is less likely to be painful. A painful lump in the armpit could be cancerous, but most lumps that are painful or tender have a different cause.

Regardless of the lump’s characteristics or accompanying symptoms, it is reasonable and likely a good idea to have it checked out by a doctor if it does not resolve on its own.

Medical Reviewer Biographical Information

Dr. Waks graduated from Princeton University with a bachelor’s degree in 2006 and Harvard Medical School with a master’s degree in 2011. She completed a medical oncology fellowship at Dana-Farber/Partners CancerCare before joining the Breast Oncology Center at Dana-Farber Cancer Institute. She completed her internal medicine residency at Brigham and Women’s Hospital, where she also worked as a Chief Resident in Internal Medicine for a year.

I’d never heard of or seen anyone else in a similar situation. Thank you very much. The journey to a breast cancer diagnosis was long and winding. You’ve described exactly how I found out I had breast cancer. This is very useful information.

Stef Work
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