Explanations for a Lump Under the Armpit

Upon discovering a lump under the armpit, there are many things that might race through your mind. If you are a woman, then you’re probably starting to worry that you might have breast cancer or another terrible condition. If you’re a man, then you may have less fear about breast cancer but may be concerned about lymphoma. Take a look below to learn about a few of the possible explanations behind a lump under the armpit.


Cysts can crop up anywhere in the body, and the armpit certainly isn’t an exception. A cyst is a mass that can be made of any tissue or a combination of tissue and fluid. Cysts that form in the underarm area are usually the result of skin cells that fail to slough away from the body which can act as blockage to pores and sweat glands in the armpit. Men and teenage girls are more likely to experience a cyst in this area; however it can affect anyone at any age. Shaving the underarms or failing to scrub them clean on a regular basis can cause infection or irritation that eventually leads to the development of a cyst under the skin. The good news is that cysts are more or less harmless to the body and they usually disappear on their own, although the amount of time it takes for a cyst to dissolve can vary from person to person.

Sometimes cysts do not disappear or in fact may become larger over time. In this case, as well as in the event that the cyst becomes painful, causes irritation to the sensitive armpit area, or begins to push on nearby lymph nodes, one might choose to have the cyst surgically removed. Cysts can sometimes be prevented by keeping the underarm area free of buildup. An exfoliating body wash can work well to remove excess skin cells and deodorant buildup.


Infection is a condition that everyone will experience at some point in our lives, and in some cases the infection can lead to a resulting lump under the armpit. Some of the most likely infections that cause this are bacterial infections of the arm and the breast, fungal infection known as sporotrichosis, and viral infections such as chickenpox, mononucleosis, and shingles. Bacterial infection of the breast is most common in nursing mothers and is often caused by the staphylococcus aureus bacteria—a bacteria that is naturally present on human skin. When a wound in the breast, such as dry or cracked skin of the nipple, allows this bacteria to enter the body the fatty tissues within the breast become an ideal place for the bacteria to spread, which leads to infection. A natural reaction by the body is inflammation, which causes redness and swelling. Sometimes the swelling can push against milk ducts which causes a lump under the skin that may or may not be visible to the eye but is certainly detectable by touch.

The fungal infection called sporotrichosis can easily be found in the armpit area due to its close proximity to the arm. This type of infection is usually caught when a fungus typically found on plants is allowed to enter the body. This can happen by physically touching the fungus or by inhaling the spores, and is very common in people who handle plant and soil matter. The symptom of sporotrichosis involves red, painless lumps under the skin that eventually turn into ulcers. Luckily this condition can be treated with an antifungal medication!

Viral infections like the chicken pox, shingles, and mononucleosis (“mono”) are all known to produce bumps or lumps that vary in size, although they are not limited to the armpit area. As you probably already know, there is little you can do to treat a viral infection and the resulting lumps and bumps that they may produce. Viruses simply have to live out the course of the infection until your body learns how to kill it off. Any lumps that have resulted from the virus will usually clear up within a week or two after the infection.


An abscess could also explain a lump under the armpit. An abscess is somewhat like a cyst, except that instead of being a mass, air-filled, or fluid filled bubble, an abscess is a pocket that is filled with puss and is the direct result of an infection. If you shave your armpits then you are much more likely to acquire an abscess as the result of an infection occurring through a cut or wound caused by the razor. An abscess can be quite painful, especially in the armpit where heat, sweat, and friction can cause further irritation to the puss-filled pocked. If an abscess is indeed the cause behind a lump under the armpit then it can be treated by draining the puss, although an antibiotic may also be prescribed to get rid of any lingering infection that might have caused the abscess in the first place.  


Unfortunately there is also the possibility of cancer being present, namely lymphoma or breast cancer. Lymphoma is a type of cancer that produces lumps in the neck, armpits, or groin. These lumps are actually enlarged lymph nodes that have been affected by cancerous cells. Other symptoms that can accompany lymphoma include fatigue, unexplained rapid weight loss, itchiness felt all over the body, lack of desire to eat, fatigue, and night-sweating.

Breast cancer is another possibility and is typically suspected when a lump is found in the fatty tissues of the breast. For most women the fatty breast tissue can extend very close to the armpit. This lump is usually the first sign of breast cancer and may be detected through self-examination, felt by a partner, or noticed during a mammogram screening. Other possible symptoms include dimpling in the skin of the breast or nipple, scaling or thickening of the skin, and pain in the breast or nipple.

If you are ever unsure about a lump under the armpit then you should probably make it a point to see your doctor.