what is central nervous system lymphoma
1 Primary central nervous system (CNS) lymphoma is a disease in which malignant (cancer) cells form in the lymph tissue of the brain and/or spinal cord. 2  Having a weakened immune system may increase the risk of developing primary CNS lymphoma.ymphoma is a disease in which malignant (cancer) cells form in the lymph system. The lymph system is part of the immune system and is made up of the lymph, lymph vessels, lymph nodes, spleen, thymus, tonsils, and bone marrow. Lymphocytes (carried in the lymph) travel in and out of the central nervous system (CNS).