Lymph nodes are small, bean-shaped structures important to the body’s immune system. They are located throughout the body, including the neck, armpits, and groin. Their primary role is filtering lymph fluid, a clear substance that carries nutrients and removes waste. Lymph nodes trap harmful substances like bacteria, viruses, and abnormal cells, preventing their spread and helping the body fight illness.
The Likelihood of Cancer
When lymph nodes swell, it often raises concerns, but the vast majority are not cancerous. In adults, only about 1.1% of swollen lymph nodes seen in primary care are malignant. Even among older individuals, fewer than half of those with swollen lymph nodes will have them due to cancer. While swelling can indicate certain cancers, such as lymphoma, leukemia, or metastatic cancer that has spread from another part of the body, these instances are far less common than benign causes.
Common Non-Cancerous Causes
Swollen lymph nodes most frequently result from the body’s immune response to infections and inflammatory conditions. Common viral infections like the cold, flu, and mononucleosis often cause enlargement as the body fights illness. Bacterial infections, such as strep throat, ear infections, or skin infections, also frequently lead to noticeable swelling. In these cases, lymph nodes become larger and sometimes tender as immune cells gather within them to neutralize pathogens. Autoimmune disorders like lupus and rheumatoid arthritis can also trigger generalized swelling, reflecting an overactive immune response.
When to Seek Medical Attention
While most swollen lymph nodes resolve on their own, certain characteristics warrant medical evaluation. Lymph nodes that remain persistently swollen for more than two to four weeks, or those that are rapidly growing, should prompt a doctor’s visit. Nodes that feel very hard, rubbery, or are fixed to underlying tissue rather than being movable under the skin are also concerning signs. Additional symptoms accompanying swollen nodes, such such as unexplained weight loss, night sweats, persistent fever, or fatigue, also indicate the need for professional assessment. Swollen lymph nodes located above the collarbone are particularly worrisome for malignancy and should always be investigated.
The Diagnostic Journey
The diagnostic process for swollen lymph nodes typically begins with a thorough medical history, including when the swelling started and any other symptoms. A physical examination follows, where the doctor checks the size, tenderness, warmth, and texture of the lymph nodes, as well as examining other areas of the body. Depending on the initial findings, several tests may be ordered to help determine the cause. Blood tests, such as a complete blood count, can help identify signs of infection or other disorders like leukemia. Imaging studies, including ultrasound, X-rays, or CT scans, may be used to visualize the lymph nodes and surrounding structures or to find potential sources of infection or tumors.
If the cause remains unclear or if there are specific concerns, a lymph node biopsy may be performed. This procedure involves removing a sample of tissue from the lymph node, either with a needle (fine-needle aspiration) or by surgically removing the entire node, for microscopic examination to definitively diagnose cancer or other serious conditions.