Myeloid leukemia and normal hematopoiesis. Acute myeloid leukemia (AML; red box) is a hematological disease characterized by a block in differentiation and promotion of proliferation or survival. Recurrent genetic abnormalities include t(8;21)(q22;q22), inv(16)(p13.1q22), t(16;16)(p13.1q22), t(15;17)(q22;q21), and t(9;11)(p22;q23). Chronic myeloid leukemia (CML; green box) is characterized as a stem cell disease with hyperplastic myeloid cells, including both immature and mature myeloid cells. The disease is defined by occurrence of the BCR-ABL fusion gene in the Philadelphia chromosome. Juvenile myelomonocytic leukemia (JCMML) and chronic myelomonocytic leukemia (CMML) (blue box) are hematological diseases with features of a myeloproliferative neoplasm and a myelodysplastic syndrome. Characteristics are peripheral blood monocytosis > 1 × 109/l, no Philadelphia chromosome or BCR-ABL fusion gene, no rearrangement of platelet-derived growth factor receptor alpha polypeptide, or platelet-derived growth factor receptor beta polypeptide, and > 20% blasts in the blood and bone marrow. The figure was kindly provided by Dr Line Wergeland, University of Bergen.