Chronic myelomonocytic leukemia diagnosis and classification

Diagnostic criteria and categories of CMML (World Health Organisation 2008)

1. Determine whether diagnostic criteria are fulfilled

All five of the following diagnostic criteria must be met:

  1. Persistent peripheral blood monocytosis >1 x109/L
  2. No Philadelphia chromosome or BCR-ABL1 fusion gene
  3. No rearrangement of PDGFRA or PDGFRB (should be specifically excluded in cases with eosinophilia)
  4. <20% blasts (including myeloblasts, monoblasts and promonocytes) in the blood and bone marrow
  5. Dysplasia in one or more myeloid lineages. If myelodysplasia absent or minimal, diagnosis can still be made if requirements 1-4 are met, and:
    • an acquired clonal cytogenetic or molecular genetic abnormality is present, or
    • the monocytosis has persisted for at least 3 months, and
    • all other causes of monocytosis have been excluded (e.g. infection, inflammation, malignancy)

2. Determine subcategories

CategoryFeatures5 yr AML risk (%)
CMML-1< 5 % blasts* in the blood and < 10% blasts* in the marrow18%
CMML-25 – 19% blasts* in the blood, OR 10 – 19% blasts* in the marrow, OR presence of Auer rods63%
* blasts includes promonocytes, monoblasts and myeloblasts

These World Health Organistation (WHO) criteria for the diagnosis of chronic myelomonocytic leukemia (CMML) were published in the fourth edition of the WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues.1