What Causes Swollen Lymph Nodes Under the Arm?
Swollen lymph nodes under the arm, also known as axillary lymphadenopathy, can arise from a wide range of underlying conditions—ranging from benign and temporary issues to more serious medical concerns. These small, bean-shaped glands play a crucial role in the body's immune system by filtering harmful substances and helping fight infections. When they become enlarged, it often signals that the body is responding to some form of disturbance.
Common Benign Causes of Axillary Lymph Node Enlargement
One of the most frequent non-cancerous reasons for swollen armpit lymph nodes is an infection in the upper limbs or surrounding tissues. For instance, bacterial infections such as mastitis—particularly common in breastfeeding women—can lead to inflammation in the breast tissue and subsequently cause nearby lymph nodes in the armpit to swell. Other possible causes include skin infections, cuts, or insect bites on the arm or chest area, which trigger localized immune responses.
In many cases, these swellings are temporary and resolve once the underlying infection is treated with antibiotics or proper wound care. Viral illnesses like influenza or mononucleosis may also contribute to generalized lymph node enlargement, including in the axillary region.
Potential Serious Conditions Linked to Swelling
Lymphoma and Other Lymphatic Cancers
While less common, persistent or unexplained lymph node enlargement could indicate a more serious condition, such as lymphoma—a type of cancer originating in the lymphatic system. In these cases, the swelling is usually painless, progressive, and may be accompanied by systemic symptoms like night sweats, unexplained weight loss, and persistent fatigue.
Metastatic Cancer – Especially Breast Cancer
Another critical cause of axillary lymph node swelling is metastasis from solid tumors, particularly breast cancer. Since the lymphatic system in the breast drains into the axillary nodes, cancer cells can travel and accumulate there, leading to noticeable enlargement. This is why routine breast exams often include checking the armpit area for lumps or abnormal swelling.
Women undergoing breast cancer screening should pay close attention to any new or growing masses in the underarm region, even if they don't experience pain. Early detection through mammography, ultrasound, or biopsy can significantly improve treatment outcomes.
When to See a Doctor
Given the variety of potential causes—from simple infections to malignancies—it's essential to seek medical evaluation when experiencing persistent or unexplained axillary swelling. A healthcare provider will typically review your medical history, perform a physical exam, and may order diagnostic tests such as blood work, imaging (like ultrasound or MRI), or a lymph node biopsy to determine the root cause.
Warning signs that warrant prompt medical attention include: lymph nodes larger than 1 cm, hard or fixed lumps, lack of tenderness, duration longer than two weeks, or accompanying symptoms like fever, chills, or significant weight loss.
Final Thoughts
Swollen lymph nodes under the arm are not always a sign of something dangerous, but they should never be ignored—especially if they persist without a clear explanation. Understanding the possible causes empowers individuals to take timely action and seek appropriate care. Whether it's a minor infection or a more complex health issue, early diagnosis leads to better prognosis and peace of mind.