. 2022 Jun 22;36(7):1703–1719. doi: 10.1038/s41375-022-01613-1

Table 6.

Diagnostic criteria of chronic myelomonocytic leukaemia.

Prerequisite criteria

1. Persistent absolute (≥0.5 × 10⁹/ L) and relative (≥10%) peripheral blood monocytosis.

2. Blasts constitute <20% of the cells in the peripheral blood and bone marrow.^a

3. Not meeting diagnostic criteria of chronic myeloid leukaemia or other myeloproliferative neoplasms.^b

4. Not meeting diagnostic criteria of myeloid/lymphoid neoplasms with tyrosine kinase fusions.^c

Supporting criteria

1. Dysplasia involving ≥1 myeloid lineages.^d

2. Acquired clonal cytogenetic or molecular abnormality.

3. Abnormal partitioning of peripheral blood monocyte subsets.^e

Requirements for diagnosis

- Pre-requisite criteria must be present in all cases.

- If monocytosis is ≥ 1 × 10⁹/ L: one or more supporting criteria must be met.

- If monocytosis is ≥0.5 and <1 × 10⁹/ L: supporting criteria 1 and 2 must be met.

Subtyping criteria

- Myelodysplastic CMML (MD-CMML): WBC < 13 × 10⁹/L

- Myeloproliferative CMML (MP-CMML): WBC ≥ 13 × 10⁹/L

Subgrouping criteria (based on percentage of blasts and promonocytes)

CMML-1: <5% in peripheral blood and <10% in bone marrow

CMML-2: 5–19% in peripheral blood and 10-19% in bone marrow

^aBlasts and blast equivalents include myeloblasts, monoblasts and promonocytes.

^bMyeloproliferative neoplasms (MPN) can be associated with monocytosis at presentation or during the course of the disease; such cases can mimic CMML. In these instances, a documented history of MPN excludes CMML. The presence of MPN features in the bone marrow and/or high burden of MPN-associated mutations (JAK2, CALR or MPL) tends to support MPN with monocytosis rather than CMML.

^cCriteria for myeloid/lymphoid neoplasms with tyrosine kinase fusions should be specifically excluded in cases with eosinophilia.

^dMorphologic dysplasia should be present in ≥10% of cells of a haematopoietic lineage in the bone marrow.

^eBased on detection of increased classical monocytes (>94%) in the absence of known active autoimmune diseases and/or systemic inflammatory syndromes.