Leukoses chronic - the myeloid tumour arising at a level of a cell of the progenitrix, a proliferation and which differentiation lead to expansion of processes of the hemopoiesis presented (unlike acute leukoses) mainly mature and intermediate forms. This the most widespread makes 20 % of all adults of all leukoses and 5 % of all children's hemoblastoses. It is not taped racial or sexual prevalence in a case rate. It is proved, a possible role in occurrence of disease of an ionizing radiation and other exogenous mutagen factors.

Pathogenesis. At a level of very early cell of the progenitrix there is a translocation that leads to occurrence of a so-called chromosome of Philadelphia and a mutant gene bcrabl, coding fiber р210. Expansion of positive cells to an osteal brain, a peripheric blood and extramedullary areas is explainable not so much their high proliferative activity, how many expansion of a pool of the precursors who have lost sensitivity to stimulus and changes of a microenvironment. It leads to their dissimination, disturbance of production of cytokines and suppression of a normal hemopoiesis.