Chronic myelogenous leukemia

Chronic myelogenous leukemia (CML) 

Updated: 04/20/2021

© Jun Wang, MD, PhD

General features
  • Most common chronic myeloproliferative neoplasm
  • Clonal proliferation of pluripotent granular stem cells
  • All ages affected, median age 50-60
Clinical presentations
  • Insidious onset with anemia, fatigue, weight loss
  • Extramedullary hematopoiesis causing massive hepatosplenomegaly and lymphadenopathy
Clinical course
  • Chronic phase: Usually for 3-4 years, < 10% blasts in the bone marrow, readily controlled with oral medications
  • Accelerated phase: 10-19% blasts in blood or marrow, >20% basophils in blood, persistent platelet count <100K or >1000K, increasing splenomegaly or white blood cell count while on therapy, marked myelofibrosis, additional cytogenetics abnormalities, lack of response to treatment
  • Blast transformation (phase): > 20% or more blasts in marrow or blood, often death shortly
Key pathogenesis
  • Translocation resulted abnormal activation of ABL: non-receptor tyrosine kinase in nuclei, regulating cell division, adhesion, differentiation
Key Laboratory findings
  • Leukocytosis with left shift
  • Basophilia
  • Monocytosis, usually <3%
  • Low leukocyte alkaline phosphatase (LAP) score
  • Thrombocytosis
Key morphological features
Differential diagnosis
  • Acute myeloid leukemia (AML): Blasts > 20% or cytogenetic findings
  • Chronic myelomonocytic leukemia: High monocytic count
  • Chronic neutrophilic leukemia
    • Sustained proliferation of mature neutrophils
    • May be asympatomatic
    • >80% combined segmented neutrophils or bands, <10% immature granulocytes and <1% myeloblasts in peripheral blood or <5% in marrow
    • Normal morphology of monocytic and megakaryocytic series
    • CSF3R mutation in 80% pts
    • NO PDGFRA, PDGFRB, FGFR1 nor BCR-ABL
  • Thrombocythemia: No or little granulocyte or erythroid proliferation
  • Leukemoid reactions: Toxic granulation, a HIGH LAP score, an obvious cause for the neutrophilia

Genetic abnormalities
  • t(9;22) (q34;q11), Philadelphia chromosome: BCR-ABL


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