Diagnostic criteria for clonal monocytosis of undetermined significance (CMUS)
| Persistent monocytosis defined as monocytes ≥ 0.5 × 109/L and ≥ 10% of the WBC |
| Absence or presence of cytopenia (thresholds same as for MDS)* |
| Presence of at least one myeloid neoplasm associated mutation of appropriate allele frequency (ie, ≥2%)† |
| No significant dysplasia, increased blasts (including promonocytes) or morphologic findings of CMML on bone marrow examination‡ |
| No criteria for a myeloid or other hematopoietic neoplasm are fulfilled |
| No reactive condition that would explain a monocytosis is detected |
| Persistent monocytosis defined as monocytes ≥ 0.5 × 109/L and ≥ 10% of the WBC |
| Absence or presence of cytopenia (thresholds same as for MDS)* |
| Presence of at least one myeloid neoplasm associated mutation of appropriate allele frequency (ie, ≥2%)† |
| No significant dysplasia, increased blasts (including promonocytes) or morphologic findings of CMML on bone marrow examination‡ |
| No criteria for a myeloid or other hematopoietic neoplasm are fulfilled |
| No reactive condition that would explain a monocytosis is detected |
If cytopenia is present the nomenclature of CCMUS is suggested.
VAF threshold based on International Consensus Group Conference, Vienna, 2018.260
Bone marrow findings of CMML include hypercellularity with myeloid predominance, often with increased monocytes and in a proportion of cases monoblasts and/or blast equivalents (ie, promonocytes) and/or dysplasia in at least 1 lineage.