The division of chronic myelomonocytic leukemia (CMML)-1 into CMML-0 and CMML-1 according to 2016 World Health Organization (WHO) classification has no impact in outcome in a large series of patients from the Spanish group of MDS

- CMML-0 and CMML-1 have similar prognosis in patients from the Spanish Registry.
- Unlike our study, two other studies regarding prognosis report different outcomes.
- Differences in clinical/molecular factors may explain these controversial results.