Lymph nodes are small, bean-shaped organs important to the body’s immune system. They filter lymph fluid, a clear liquid containing white blood cells that fight infections. Lymph nodes are found throughout the body, often clustered in areas like the neck, groin, and armpits. Axillary lymph nodes, located in the armpit, are important due to their proximity to the breast, arm, and chest wall.
Understanding Normal Axillary Lymph Nodes
Healthy axillary lymph nodes are small, soft, and movable, often unnoticed. On imaging, a normal axillary lymph node appears oval with smooth, well-defined borders and a central fatty hilum. This fatty hilum is a distinguishing feature on imaging.
The size of a normal axillary lymph node varies, but generally, they measure less than 10 millimeters (1 centimeter) in diameter. The outer layer, known as the cortex, should be uniformly thin, measuring 3 millimeters or less.
Size is a factor, but not the only indicator of a healthy lymph node. The shape and internal structure, such as the presence of a fatty hilum and uniform cortical thickness, are also important characteristics. Minimal vascularity in the hilum, on ultrasound, is another sign of a normal node.
Reasons for Enlargement
Axillary lymph node enlargement can stem from various causes, from benign conditions to more serious diseases. When the body encounters an infection or inflammation, the lymph nodes work harder to filter out harmful substances and produce infection-fighting white blood cells, leading to swelling. This is the body’s natural response.
Common benign causes of enlarged axillary lymph nodes include bacterial and viral infections affecting the arm, breast, chest, or upper abdomen. Examples include the common cold, flu, mononucleosis, measles, rubella, or skin infections like cellulitis. Recent vaccinations, such as the COVID-19 vaccine, can also temporarily cause swelling as the immune system responds.
Other non-infectious causes include autoimmune or rheumatological diseases like lupus or rheumatoid arthritis, and granulomatous diseases such as sarcoidosis or tuberculosis. While less common, certain cancers can also lead to axillary lymph node enlargement. These include lymphomas (Hodgkin’s and non-Hodgkin’s) and metastatic spread from other cancers, with breast cancer being a frequent cause.
When to Consult a Doctor
While many instances of enlarged axillary lymph nodes resolve on their own, certain signs and symptoms warrant medical evaluation. Consult a healthcare provider if a lymph node, or several, remain enlarged for more than a few days, especially without an apparent illness. If the swelling persists for over two weeks or worsens, also seek medical attention.
Specific characteristics of an enlarged node should prompt a doctor’s visit. These include a lump that feels hard, is immobile or fixed to the skin, or is growing rapidly. Tenderness or pain without an obvious infection, or if the skin over the node appears red or inflamed, also warrants evaluation.
Accompanying symptoms suggesting a more serious condition include unexplained fever, night sweats, or unintentional weight loss. Swelling in lymph nodes in multiple body areas, such as the neck and armpits, or difficulty breathing, are additional concerning indicators. If the swollen node is not painful, this absence of pain can also be a reason for concern.
Diagnostic Steps and Management
When evaluating enlarged axillary lymph nodes, a doctor begins with a thorough physical examination and a review of your medical history and symptoms. The examination assesses the size, number, consistency (hard or spongy), mobility, and tenderness of the lymph nodes. The doctor also notes if the enlargement is unilateral (one side) or bilateral (both sides).
To determine the underlying cause, several diagnostic tests are ordered. Blood tests, such as a complete blood count (CBC), C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR), detect infection or inflammation. Imaging studies, including ultrasound, mammography, or a CT scan, provide more detailed visualization of the lymph nodes and surrounding tissues. Ultrasound is often a first-line examination.
In cases where the cause remains unclear or malignancy is suspected, a lymph node biopsy may be performed. This involves taking a small tissue sample for microscopic examination by a pathologist. The management of enlarged axillary lymph nodes depends on the identified cause, ranging from antibiotics for bacterial infections to specific treatments for autoimmune diseases or cancer.