A myelodysplastic/myeloproliferative neoplasm which is characterized by persistent monocytosis, absence of a Philadelphia chromosome and BCR/ABL fusion gene, fewer than 20 percent blasts in the bone marrow and blood, myelodysplasia, and absence of PDGFRA or PDGFRB rearrangement. The disease is chronic myelomonocytic leukemia (MONDO_0020311, a Monarch Disease Ontology id). Also known as: CMML, chronic myelomonocytic leukaemia (CMML), chronic myelomonocytic leukemia (CMML).