Biology and pathogenesis of CNS leukemia.

Despite routine preventive central-nervous-system (CNS) therapy, 5-10% of children with acute lymphoblastic leukemia continue to suffer CNS relapse. In a majority of these patients, bone marrow relapse ensues and is usually fatal. A better understanding of the biology and pathogenesis of CNS leukemia is needed to develop more effective methods of prevention and treatment of this adverse complication of acute leukemia. Concepts of the origin and proliferation of leukemic cells in the CNS are reviewed, as well postulated mechanisms of their ingress into and egress out of the CNS.