The primary lymphoma of the central nervous system (CNS) is a rare form of non-Hodgkin's lymphoma (cancer of the lymphatic system). It consists of many parts but includes spleen, tonsils, bone marrow and lymph nodes. Special white blood cells, called lymphocytes, fight infections in the primary nervous system. When these cells become cancerous, they can cause the formation of lymphomas. (It can also start in the eyes because the eyes are very close to the brain, which is called ocular lymphoma).
Primary CNS lymphoma is rare. Men are more common than women, and the mean age of diagnosed persons is 55 years. However, people with AIDS who suffer from this type of cancer are much younger, often in their thirties.