Lymphoma develops when certain white blood cells, called lymphocytes, mutate. Normally, healthy lymphocytes are the good guys: they fight infection to protect the body from life-threatening illnesses. However, when lymphocytes become cancerous, they mutate and overproduce, attacking different parts of the body.
Lymphocytes reside in lymph nodes when they aren’t needed. There are 5 major lymph nodes that are close to the skin surface, so they can be seen or felt if they are inflamed (or swollen), and there are more on the inside of the body. As lymphoma affects white blood cells and because blood is everywhere in the body, the effects of lymphoma can occur almost anywhere in the body.