A lymph node or lymph gland, is an ovoid or kidney-shaped organ of the lymphatic system, and of the adaptive immune system, that is widely present throughout the body. They are linked by the lymphatic vessels as a part of the circulatory system. Lymph nodes are major sites of B and T lymphocytes, and other white blood cells. Lymph nodes are important for the proper functioning of the immune system, acting as filters for foreign particles and cancer cells. Lymph nodes do not have a detoxification function, which is primarily dealt with by the liver and kidneys.
In the lymphatic system the lymph node is a secondary lymphoid organ. A lymph node is enclosed in a fibrous capsule and is made up of an outer cortex and an inner medulla.
Lymph nodes also have clinical significance. They become inflamed or enlarged in various diseases which may range from trivial throat infections, to life-threatening cancers. The condition of the lymph nodes is very important in cancer staging, which decides the treatment to be used, and determines the prognosis. When swollen, inflamed or enlarged, lymph nodes can be hard, firm or tender