Definition of Non-Hodgkin's lymphoma:

Non-Hodgkin's lymphoma is cancer of the lymphoid tissue, which includes the lymph nodes, spleen, and other organs of the immune system.

Causes, incidence, and risk factors:

White blood cells called lymphocytes are found in lymph tissues. Most lymphomas start in a type of white blood cells called B lymphocytes, or B cells.

For most patients, the cause of this cancer is unknown. However, lymphomas may develop in people with weakened immune systems. For example, the risk of lymphoma increases after an organ transplant or in people with HIV infection.

Non-Hodgkin's lymphoma is classified according to how fast the cancer spreads. The cancer may be low grade, intermediate grade, or high grade. Burkitt's tumor is an example of a high-grade lymphoma. There are many different types of non-Hodgkin's lymphoma.

According to the American Cancer Society, a person has a 1 in 50 chance of developing non-Hodgkin's lymphoma. Most of the time, this cancer affects adults. However, children can get some forms of lymphoma. High-risk groups include those who have received an organ transplant or who have a weakened immune system (immunosuppression).

This type of cancer is more common in men than in women.