How does leukemia invade the central nervous system?

Prolongation of survival of children with acute leukemia by systemic therapy has brought a marded increase in incidence of CNS leukemia. In mice inoculated with leukemia cells, CNS i nfiltrates are rare unless life is prolonged by chemotherapy. Available evidence seems to indicate that leukemic cells in the CNS in most cases originate in bone marrow or lymph nodes.