Leukaemia is the general name given to a group of cancers that develop in the bone marrow. Leukaemia 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 leukaemia originate in developing white cells. In a small number of cases leukaemia develops in other blood-forming cells, for example in developing red cells or developing platelets. Leukaemia can also be either myeloid or lymphocytic. The terms myeloid and lymphocytic refer to the types of cells in which the leukaemia first started. Myeloid stem cells develop into red cells, white cells (neutrophils, eosinophils, basophils and monocytes) and platelets. Lymphoid stem cells develop in two other types of white cells called T-lymphocytes and B-lymphocytes.
Both adults and children can develop leukaemia but certain types are more common in different age groups.
