Finding a lump under your armpit can feel alarming, and yet most of the time it is explainable and usually not serious at all. So if you spotted a small lump sort of low in the armpit, or you noticed a larger one that appeared more suddenly, you will probably want to figure out what it might be, and then decide when it is smart to see your doctor. Below is a loose overview of the most typical causes, the warning signs, and how healthcare professionals can help you with different imaging options that are available for a lump under the armpit.

What is the most common reason for a lump under the armpit in both women and men?

Lymph nodes, those little glands that help your immune system, live in the armpit area. These nodes swell in response to an infection, inflammation, and any changes within the body. A lump under the armpit in females, or a lump under the armpit in males, is often about the same kind of causes, and most of the time it is not malignant or anything cancer-like.

Common Causes of a Lump Under the Armpit

• A smaller bump in the armpit is most frequently tied to swollen lymph nodes. That can happen when your immune system is busy dealing with something, like a cold, the flu, a skin infection, or even a seemingly “minor” cut on the arm. In these situations, the lump will often fade on its own once the infection clears, and the swelling goes down. 
• Another fairly common idea is ingrown hairs or skin irritations, especially in places that get shaved. You may see a small red bump that seems to sit just near the skin’s surface. This can appear in both sexes, and it generally calms down with time if you stick to gentle skincare and try not to keep rubbing the area.
• In the softer tissue of the armpit, it can happen that there are non-cancerous lumps, like cysts, or sometimes lipomas. A cyst is a closed sac under the skin, and a lipoma is a slow-growing mass of fat. Both are soft and movable and are usually not painful.
• The swelling of the lymph nodes around the armpit can be temporary and it comes from an allergic reaction or from the body’s response to a vaccination, sort of like a delayed kind of signal. This is pretty well documented after certain shots given in the upper arm, and it usually calms down within a few weeks.

When is a lump in the armpit more concerning? 

Most armpit lumps are generally harmless, but some signs mean you should not wait for it to settle. There are a few clues; if you recognize them can help you decide when it’s worth getting checked, not just hoping it fades. For example, if you notice a big bump under the armpit, or if it stays put for a long time without any movement, there are a few features to pay attention to.

Signs of trouble requiring medical care.

• If the lump feels hard, irregular or fixed in place and is getting bigger, it should be seen by a doctor. [2]
• Any lumps that come with symptoms that are unexplained, like a loss in weight, night sweats, constant tiredness, or fever, should be discussed with a health care provider.
• When these whole-body symptoms come with a swollen armpit node, they can be a sign that the lymph nodes are reacting to something that needs investigation. [2]
• If an unexplained armpit lump persists for more than two weeks, continues growing, or does not begin to improve, arrange an evaluation with your healthcare provider. Do not delay getting it checked if it feels hard or fixed, or if you have other unexplained symptoms. [2]
• For women, an armpit lump can sometimes be a sign of breast cancer, so it should be checked by a healthcare provider promptly. [1]

Are Swollen Lymph Nodes Under the Armpit connected to cancer?

Yes, sometimes, swollen lymph nodes under the armpit are related to some types of cancer, such as breast cancer. Breast cancer can sometimes spread to the lymph nodes under the arm, causing them to become enlarged and form a lump under the armpit. Most lumps in the armpit area, however, are not associated with cancer. Any unexplained or persistent lump should be evaluated by a healthcare professional. [1]

Common benign cause	Potentially serious causes
Swollen lymph nodes due to infections	Lymphoma and other cancers affecting lymph nodes
Ingrown hairs and folliculitis	Persistent or unexplained lymph node enlargement
Cysts and lipomas	Lymph node swelling with unexplained weight loss, night sweats, or fever
Temporary swelling after vaccination	Cancer that has spread to the underarm lymph nod

These are possible causes only; a lump cannot be diagnosed by how it looks or feels.

How do health care providers determine the cause of armpit lumps?

When you visit your doctor about a lump under your armpit,  either a small lump under armpit that’s been there for weeks or a large lump under your armpit that you noticed recently your doctor will go through the evaluation process. The goal is to better understand the possible cause of the lump and determine whether additional testing is needed. Your health provider will answer all your concerns about why do I have a lump under my armpit. 

Physical Exam and Med Evaluation

• Often, an initial physical examination is the first step. Your doctor will examine the lump to check whether it is movable, hard or tender, and will ask you about any recent infections or illnesses, vaccinations, and when the lump appeared. A physical examination helps physicians evaluate the characteristics of the lump and possible underlying causes.  
• Imaging tests may be recommended when a physical examination alone cannot determine the cause of the lump. Ultrasound of the armpit is usually the first imaging test for evaluating a new armpit lump you can feel. Depending on the patient’s age, symptoms, and examination findings, diagnostic mammography may also be recommended for women. [3] CT is sometimes used if more detail is needed.

Depending on the examination and imaging findings, a healthcare provider may recommend additional tests, such as blood tests or a biopsy, to determine the cause of a persistent or suspicious lump. The tests are conducted by specialist medical providers and are used to further detail the cause of persistent or problematic lumps.

Conclusion  

Whether you notice a lump under the armpit in a woman or a man, it is important not to ignore unexplained changes. Most armpit lumps are caused by benign conditions, but a healthcare professional can evaluate the lump and determine whether further testing is needed. If the lump persists, grows larger, feels hard or fixed, or occurs alongside unexplained symptoms, arrange a medical evaluation.

ViaScan of Las Colinas offers CT-based imaging services. For a new armpit lump, ultrasound is usually the first imaging test, so ask your doctor which imaging is right for you.

References

[1] MedlinePlus (U.S. National Library of Medicine) — Swollen lymph nodes.https://medlineplus.gov/ency/article/003097.htm

[2] American College of Radiology — ACR Appropriateness Criteria: Imaging of the Axillahttps://acsearch.acr.org/docs/3158165/Narrative/

[3] NHS — Lumpshttps://www.nhs.uk/conditions/lumps/