What Is Non-Hodgkin Lymphoma?

Non-Hodgkin lymphoma is cancer that begins in cells of the immune system. The immune system fights infections and other diseases.
The lymphatic system is part of the immune system. The lymphatic system includes the following:

• Lymph vessels: The lymphatic system has a network of lymph vessels. Lymph vessels branch into all the tissues of the body.
• Lymph: The lymph vessels carry clear fluid called lymph. Lymph contains white blood cells, especially lymphocytes such as B cells and T cells.
• Lymph nodes: Lymph vessels are connected to small, round masses of tissue called lymph nodes. Groups of lymph nodes are found in the neck, underarms, chest, abdomen, and groin. Lymph nodes store white blood cells. They trap and remove bacteria or other harmful substances that may be in the lymph.
• Other parts of the lymphatic system: Other parts of the lymphatic system include the tonsils, thymus, and spleen. Lymphatic tissue is also found in other parts of the body including the stomach, skin, and small intestine.