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WHO Classification of Tumours
Chronic myelomonocytic leukaemia
Tumours of haematopoietic and lymphoid tissues


Chronic myelomonocytic leukaemia (CMML) is a clonal haematopoietic malignancy that is characterized by features of both a myeloproliferative neoplasm and a myelo­dysplastic syndrome. It is characterized by: 1) persistent monocytosis >1x109/L in the peripheral blood (PB); 2) absence of a Philadelphia (Ph) chromosome and BCR-ABL1 fusion gene; 3) no rearrangement of PDGFRA or PDGFRB (should be specifically excluded in cases with eosinophilia); 4) fewer than 20% blasts (promonocytes are considered as blast equivalents) in the PB and bone marrow (BM); and 5) dysplasia involving one or more myeloid lineages. However, if convincing myelo­dysplasia is not present, the diagnosis of CMML can still be made if the other requirements are met, and an acquired, clonal cytogenetic or molecular genetic abnormality is present in the BM cells, or if the monocytosis has persisted for at least 3 months and all other causes of monocytosis, such as the presence of malignancy, infection or inflammation, have been excluded. CMML is further subdivided into two subsets, CMML-1 and CMML-2, depending on the number of blasts plus promonocytes in the PB and BM. The clinical, haematological and morphological features of CMML are heterogeneous, and vary along a spectrum from predominantly myelodysplastic to mainly myeloproliferative in nature. In contrast with the BCR-ABL1 negative myeloproliferative neoplasms, JAK2 V617F mutation is uncommon in CMML
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Johan MF, Goodeve AC, Bowen DT, Frew ME, Reilly JT (2005)
JAK2 V617F Mutation is uncommon in chronic myelomonocytic leukaemia.
Br J Haematol 130: 968

Click to access Pubmed
Steensma DP, Dewald GW, Lasho TL, Powell HL, McClure RF, Levine RL, Gilliland DG, Tefferi A (2005)
The JAK2 V617F activating tyrosine kinase mutation is an infrequent event in both "atypical" myeloproliferative disorders and myelodysplastic syndromes.
Blood 106: 1207-9


> Related Topics
Chronic myelogenous leukaemia, BCR-ABL1 positive
Atypical chronic myeloid leukaemia, BCR-ABL1 negative
Acute myelomonocytic leukaemia
Myeloid and lymphoid neoplasms with eosinophilia and abnormalities of PDGFRA, PDGFRB or FGFR1
Overview: Myelodysplastic syndromes/neoplasms
Introduction: Myeloid Neoplasms

Diagnostic criteria for chronic myelomonocytic leukaemia
Diagnostic criteria for chronic myelomonocytic leukaemia