Clusters of these lymph nodes are found in the underarm, groin, neck, and abdomen. A colorless, watery fluid, called lymph, which contains infection-fighting cells, moves through the system and is filtered by the nodes. Other parts of the lymph system are the spleen, thymus, tonsils, and bone marrow. Lymph tissue is also found in other parts of the body including the stomach, intestines, and skin. Lymphomas, like other cancers, are diseases of the cells within the body.
Cancer involving the lymph system cells causes cells to grow rapidly and without order.
This creates too many cells growing together to form tumors. An estimated 62,300 new cases of lymphoma will be diagnosed in 2000, including 7,400 cases of Hodgkin's disease and 54,900 cases of non-Hodgkin's lymphoma. Since the early 1970's, incidence rates for non-Hodgkin's lymphoma have increased dramatically, making it one of the fastest rising cancers in the United States. Despite remarkable strides in understanding the biology of lymphomas, its causes remain unknown. The most common symptom of lymphoma is a painless swelling of the lymph nodes in the neck, underarm, and groin.