Causes of Swollen Lymph Nodes in the Armpit: What You Need to Know

Swollen lymph nodes in the armpit, also known as axillary lymphadenopathy, can be a concerning symptom that warrants medical evaluation. One of the primary conditions doctors investigate is the presence of malignancies, particularly breast cancer. The lymphatic system in the armpit drains fluid from the breast and surrounding areas, making it a common site for cancer cells to spread. However, breast cancer is not the only type of cancer associated with this condition—lymphomas, such as Hodgkin's or non-Hodgkin's lymphoma, and metastases from other organ cancers (like lung or melanoma) may also lead to enlarged armpit lymph nodes.

Common Infections Linked to Armpit Lymph Node Enlargement

Infections are another major cause of swollen lymph nodes under the arm. When the body fights off an infection, nearby lymph nodes often swell as part of the immune response. For instance, skin infections or injuries in the arm or hand—such as cuts, insect bites, or abscesses—can trigger localized swelling in the axillary region. Similarly, acute mastitis, a painful breast infection commonly seen in breastfeeding women, frequently results in tender, enlarged lymph nodes in the armpit.

Viral and Bacterial Infections to Consider

Certain viral infections, including mononucleosis (caused by Epstein-Barr virus) or even common upper respiratory viruses, may indirectly lead to lymph node swelling in the armpits. Additionally, bacterial infections like tuberculosis can cause a specific condition called scrofula or tuberculous lymphadenitis, which affects the lymph nodes throughout the body, including those in the axilla. These infections typically present with additional symptoms such as fever, night sweats, fatigue, and weight loss.

Autoimmune and Inflammatory Conditions

Beyond cancer and infections, autoimmune diseases are another important category to consider. Conditions such as rheumatoid arthritis, systemic lupus erythematosus (SLE), and Sjögren's syndrome can lead to generalized lymphadenopathy, including in the armpits. In these cases, the immune system mistakenly attacks healthy tissues, triggering inflammation and lymph node enlargement.

It's important to note that while occasional, mild swelling may resolve on its own—especially after a minor infection—persistent, painless, or progressively enlarging lymph nodes should always be evaluated by a healthcare provider. Diagnostic tools such as ultrasound, blood tests, or even a biopsy may be necessary to determine the underlying cause.

When to Seek Medical Attention

If you notice lumps in your armpit that last more than two weeks, feel hard or immovable, or are accompanied by unexplained symptoms like fever, fatigue, or weight loss, consult a physician promptly. Early diagnosis significantly improves outcomes, especially when serious conditions like cancer or chronic infections are involved.

In summary, while swollen axillary lymph nodes are often benign and linked to treatable causes like infections, they can sometimes signal more serious underlying health issues. Staying informed and proactive about changes in your body is key to maintaining long-term wellness.