Diagnostic criteria for chronic myelomonocytic leukemia (CMML)
| Monocytosis defined as monocytes ≥ 0.5 × 109/L and ≥ 10% of the WBC |
| Cytopenia (thresholds same as MDS)* |
| Blasts (including promonocytes) < 20% of the cells in blood and bone marrow |
| Presence of clonality: abnormal cytogenetics and/or presence of at least one myeloid neoplasm associated mutation of at least 10% allele frequency† |
| In cases without evidence of clonality, monocytes ≥ 1.0 × 109/L and > 10% of the WBC, and increased blasts (including promonocytes),‡ or morphologic dysplasia, or an abnormal immunophenotype consistent with CMML would be required for its diagnosis. |
| Bone marrow examination with morphologic findings consistent with CMML (hypercellularity due to a myeloid proliferation often with increased monocytes), and lacking diagnostic features of acute myeloid leukemia, MPN or other conditions associated with monocytosis§ |
| No BCR::ABL1 or genetic abnormalities of myeloid/lymphoid neoplasms with eosinophilia and tyrosine kinase gene fusions |
| Monocytosis defined as monocytes ≥ 0.5 × 109/L and ≥ 10% of the WBC |
| Cytopenia (thresholds same as MDS)* |
| Blasts (including promonocytes) < 20% of the cells in blood and bone marrow |
| Presence of clonality: abnormal cytogenetics and/or presence of at least one myeloid neoplasm associated mutation of at least 10% allele frequency† |
| In cases without evidence of clonality, monocytes ≥ 1.0 × 109/L and > 10% of the WBC, and increased blasts (including promonocytes),‡ or morphologic dysplasia, or an abnormal immunophenotype consistent with CMML would be required for its diagnosis. |
| Bone marrow examination with morphologic findings consistent with CMML (hypercellularity due to a myeloid proliferation often with increased monocytes), and lacking diagnostic features of acute myeloid leukemia, MPN or other conditions associated with monocytosis§ |
| No BCR::ABL1 or genetic abnormalities of myeloid/lymphoid neoplasms with eosinophilia and tyrosine kinase gene fusions |
A small proportion of cases may show only borderline or no cytopenia usually in early phase disease.
Based on International Consensus Group Conference, Vienna, 2018.260
Increased blasts: ≥5% in the bone marrow and/or ≥2% in the peripheral blood.
For cases lacking bone marrow findings of CMML, a diagnosis of CMUS could be considered. If cytopenia is present, a diagnosis of CCMUS could be entertained. In these diagnostic settings, however, an alternative cause for the observed monocytosis would have to be excluded based on appropriate clinicopathologic correlations.