text: The relevance of extramedullary hemopoiesis to the staging of chronic myeloid leukemia.
  In chronic myeloid leukemia (CML) the spleen and the liver can lodge, trap and release a high proportion of leukemic cells, and are active sites of (leukemic) hemopoiesis throughout the disease. Evidence is provided that spleen and liver volume have a prognostic value, and that marrow, spleen, and liver differ as to cell composition, cell kinetic patterns, functional cell characters, and cell karyotype. In the majority of the patients, extramedullary hemopoiesis seems to be more abnormal than marrow hemopoiesis, supporting the hypothesis that spleen and/or liver can play an important role in the evolution of CML towards the blastic metamorphosis. However, present information on extramedullary hemopoiesis does not allow to identify specific patterns and to establish its relevance to the course of the disease.