Chronic Myeloid Leukemia: Classification

WHO classification of chronic myeloid leukemia/myeloproliferative neoplasia.

Chronic phase
Accelerated phase
  • 15-19% blasts in blood or bone marrow or
  • ≥ 20 % basophilia in the blood (increase in basophilic granulocytes/subgroup of leukocytes (white blood cells)) – indication that the severity of the disease is increasing, or
  • Persistent (continuing), therapy-independent thrombocytopenia (pathological reduction in platelets/platelets: < 100 x 109/L) or
  • Development of additional chromosomal aberrations (abnormalities) in Ph+ cells (Philadelphia chromosome) despite treatment or
  • Thrombocytosis (abnormal proliferation of platelets (blood platelets); > 1,999 x 109/L) that does not respond to therapy or
  • Progressive splenomegaly (progressive splenomegaly) and rising leukocytes that do not respond to therapy
Blast crisis
  • ≥ 20% blasts in blood or bone marrow or
  • Evidence of extramedullary blasts (outside the spleen) or
  • Large blast foci or clusters detectable in bone marrow biopsy.

European LeukemiaNet classification (ELN classification) of chronic myeloid leukemia/myeloproliferative neoplasia.

Chronic phase
Accelerated phase
  • 15-29% blasts in blood or bone marrow or
  • ≥ 30 % blasts + promyelocytes (precursor form of granulocytes/subgroup of leukocytes (white blood cells)) in blood or bone marrow (blasts < 30 %) or
  • ≥ 20 % basophilia in the blood (proliferation of basophilic granulocytes) or
  • Persistent (persisting), therapy-independent thrombocytopenia (pathological reduction of platelets/platelets; < 100 x 109/L) or
  • Development of additional chromosomal aberrations (abnormalities) in Ph+ cells (Philadelphia chromosome) despite treatment.
Blast crisis
  • ≥ 30% blasts in blood or bone marrow or
  • Evidence of extramedullary blasts (outside the spleen).