Definition of Non-Hodgkin's lymphoma:

Non-Hodgkin's lymphoma is cancer that starts in the lymphoid tissue. Such tissue makes up 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.

For most patients, the cause of the cancer is unknown. However, lymphomas may develop in people with weakened immune systems. For example, after an organ transplant.

Non-Hodgkin's lymphoma is grouped, or staged, 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 CLL. High-risk groups include those who have received an organ transplant or who have a weakened immune system (immunosuppression). The cancer is more common in men than women.