Chronic myelomonocytic leukemia (CMML) is classified by the WHO as a mixed myelodysplasia and myeloproliferative disorder. It can be defined based on hematologic and cytologic findings.


General features:

(1) persistent monocytosis > 1,000 per µL in the peripheral blood

(2) < 20% blasts in blood or bone marrow

(3) one of the following:

(3a) dysplasia in one or more marrow cell lines

(3b) the monocytosis has lasted for at least 3 months and all other causes of monocytosis have been excluded

(3c) there is an acquired, clonal cytogenetic abnormality in the bone marrow



• Blasts include myeloblasts, monoblasts and promonocytes.



(1) Philadelphia chromosome

(2) BCR/ABL fusion genes

(3) >= 20% blasts in blood or bone marrow (indicates AML)


Subtypes of CMML:

(1) CMML-1

(2) CMML-2

(3) CMML with eosinophilia





< 5% blasts in the peripheral blood AND < 10% blasts in the bone marrow AND no Auer rods


(a) 5-19% blasts in the peripheral blood, or (b) 10-19% blasts in the bone marrow or (c) Auer rods present with blast count < 20% in bone marrow or peripheral blood

CMML-1 or CMML-2 with eosinophilia

as above, with absolute eosinophil count > 1,500 per µL


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