(limf node) A small bean-shaped structure that is part of the body's immune system. Lymph nodes filter substances that travel through the lymphatic fluid, and they contain lymphocytes (white blood cells) that help the body fight infection and disease. There are hundreds of lymph nodes found throughout the body.

Are lymph nodes serious?

No, swollen lymph nodes aren't fatal. Alone, they're simply a sign that your immune system is fighting an infection or illness. However, in rare cases, swollen lymph nodes can point to serious conditions, such as cancer of the lymphatic system (lymphoma), which could potentially be fatal.

When should you worry about a swollen lymph node?

When to see a doctor

See your doctor if you're concerned or if your swollen lymph nodes: Have appeared for no apparent reason. Continue to enlarge or have been present for two to four weeks. Feel hard or rubbery, or don't move when you push on them.