Lymph nodes

A lymph node is an oval-shaped organ of the lymphatic system. Lymph nodes are distributed widely throughout the body and are linked by lymphatic vessels. Lymph nodes are clustered in the neck, armpit (axilla), and groin. Lymph nodes act as filters or traps for foreign particles and are important in the proper functioning of the immune system. They are packed tightly with the white blood cells called lymphocytes and macrophages.

Lymph nodes become inflamed or enlarged in various infections and diseases, which may range from trivial (e.g., a throat infection) to life-threatening (e.g., cancer). In the latter, the condition of lymph nodes is so significant that it is used for cancer staging, prognosis, and decisions on the mode of treatment.

When swollen, inflamed or enlarged, lymph nodes can be hard, firm or tender. Swollen lymph nodes can be biopsied. Certain diseases affect lymph nodes with characteristic consistency and location.