Leukemia is the general name given to a group of cancers that develop in the bone marrow. Leukemia originates in developing blood cells that have undergone a malignant change. This means that they multiply in an uncontrolled way and do not mature properly, leaving them unable to function as they should. Most cases of leukemia originate in developing white cells. In a small number of cases leukemia develops in other blood-forming cells, for example in developing red cells or developing platelets. Leukemia can also be either myeloid or lymphocytic. The terms myeloid and lymphocytic refer to the types of cells in which the leukemia first started. Myeloid stem cells develop into red cells, white cells (neutrophils, eosinophil’s, basophils and monocytes) and platelets. Lymphoid stem cells develop in two other types of white cells called T-lymphocytes and B-lymphocytes. There are several different types and subtypes of leukemia. Leukemia can be either acute or chronic. Under normal conditions the bone marrow contains a small number of immature cells, called blast cells.  These immature blast cells develop into mature white cells, red cells and platelets which are eventually released into the blood stream. In people with acute leukemia, the diseased bone marrow produces an excessive number of abnormal blast cells, called leukemic cells.  These cells accumulate in the bone marrow interfering with the production of normal blood cells. Acute leukemia develops and progresses quickly and therefore needs to be treated as soon as it is diagnosed.