Leukocytes develop fiom stem cells located in the bone marrow. During leukocyte maturation, cells become committed to specific cell types and develop through multiple stages of differentiation and along two distinct cell lines. Leukaemia occurs within this maturation process. A damaged single cell is capable of indefinite self-renewal, and produces poorly differentiated blast cells. Leukaemic blast cells have no functional purposes and disrupt functioning by replacing the normal bone marrow element and infiltrating various organs.