Lymph Nodes (definition of)

The lymph nodes are small, bean-shaped glands that play an essential role in the body's immune system. With over five hundred of these in the human body, most lymph nodes are concentrated in the armpits, the neck, and groin.

Lymph nodes are responsible for filtering lymphatic fluid and trapping pathogens such as bacteria or viruses. These are then eliminated with specialized white blood cells known as lymphocytes. Along with macrophages, these work together in order to trap and remove invading pathogens. During bouts of infection, lymph nodes may become enlarged or swollen due to the production of additional white blood cells.

Cancer of the lymph nodes is known as lymphoma. Because cancer cells can travel through the lymphatic system, lymph nodes are often a secondary site for many types of cancer, including mesothelioma.