Atypical chronic myeloid leukemia (aCML)

  • Method:
  • Anticoagulant:
  • Recommendation:
  • Method:
    Cytomorphology
  • Anticoagulant:
    EDTA
  • Recommendation:
    obligatory
  • Method:
    Immunophenotyping
  • Anticoagulant:
    EDTA or Heparin
  • Recommendation:
    facultative
  • Method:
    Chromosome analysis
  • Anticoagulant:
    Heparin
  • Recommendation:
    obligatory
  • Method:
    FISH
  • Anticoagulant:
  • Recommendation:
    no
  • Method:
    Molecular genetics
  • Anticoagulant:
    EDTA or Heparin
  • Recommendation:
    obligatory

Based on the current guidelines and the current state of research, there are different diagnostic recommendations for patients with atypical chronic myeloid leukemia. We have summarized the most important information on classification and diagnostic methods at the MLL for you.

aCML: Classification

According to the 2017 WHO classification, aCML, BCR::ABL1-negative is categorized as a myelodysplastic/myeloproliferative neoplasm (MDS/MPN) (Swerdlow et al. 2017).

Diagnostic criteria:

  • Peripheral blood (PB) leukocytosis (≥ 13 x109/L), due to increased numbers of neutrophils and their precursors, with neutrophil precursors constituting ≥ 10% of the leukocytes
  • Dysgranulopoiesis
  • No or minimal basophilia (basophils < 2% of leukocytes in PB)
  • No or minimal monocytosis (monocytes < 10% of leukocytes in PB)
  • Hypercellular bone marrow with granulocytic proliferation and dysplasia; with or without dysplasia in the erythroid and megakaryocytic lineages
  • < 20% blasts in PB and bone marrow
  • Exclusion of a PDGFRA, PDGFRB or FGFR1 rearrangement as well as a PCM1::JAK2 rearrangement
  • Exclusion of a BCR::ABL1-positive CML, PMF, PV or ET

aCML: Diagnostic methods and their relevance

aCML: Prognosis

A leukocyte count of >50x109/L has been described as a prognostically negative parameter in aCML in several studies (Onida et al. 2002, Breccia et al. 2006, Wang et al. 2014). In some of these studies, age >65 years, female gender and hemoglobin level <10 g/dL were also prognostically unfavorable. In addition, a SETBP1 mutation was shown to have a negative impact (Piazza et al. 2013). 30-40% of patients with aCML show transformation into AML (Wang et al. 2014).

aCML: Recommendation

It should be noted that according to WHO 2017, when a CSF3R mutation is detected, CNL should be excluded morphologically as part of the differential diagnoses. Similarly, if a JAK2, CALR, or MPL mutation is detected, an accelerated phase of MPN should be excluded based on history.

In contrast, according to WHO 2017, the presence of a SETBP1 or ETNK1 mutation supports the diagnosis of atypical CML.

Status: June 2022

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