In the 2008 WHO classification, myeloproliferative disorders initially called ‘Chronic MyeloProliferative Diseases’ (CMPD) were reclassified as ‘MyeloProliferative Neoplasms’ (MPN) with nine entities and were split into BCR::ABL1-positive MPN (CML) and BCR::ABL1-negative MPN. This evidence concerns the gene ABL1 and myeloproliferative neoplasm.