The lymphatic system is a network of lymphoid organs and lymphatic vessels. It transports lymph fluid and helps to clear toxins and other waste from the body’s tissues. Lymphocytes use the lymphatic system to circulate throughout the body, but it can also facilitate the spread of cancer cells. A lymph node is an oval-shaped organ of the lymphatic system, distributed widely throughout the body including the armpit and stomach and linked by lymphatic vessels. Lymph nodes are major sites of B, T, and other immunity cells. 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 also have clinical significance. They become inflamed or enlarged in various infections and diseases which may range from trivial, such as a throat infection, to life-threatening such as cancers. In the latter, the condition of lymph nodes is so significant that it is used for cancer staging, which decides the treatment to be employed, and for determining the prognosis. When swollen, inflamed or enlarged, lymph nodes can be hard, firm or tender. The lymph system is an important part of the immune system, the body's defense system against disease. The lymph nodes filter lymph fluid as it flows through them, trapping bacteria, viruses, and other foreign substances, which are then destroyed by special white blood cells called lymphocytes. When lymph nodes swell in two or more areas of the body, it is called generalized lymphadenopathy.