MECOM and acute myeloid leukemia: The ICC lists all AML subtypes without subcategorisation and retains the previous name AML, NOS for those AMLs without defining genetic abnormalities.2 Both classifications expand the KMT2A and MECOM rearrangement categories to allow for many fusion partners, and the ICC includes defined partner genes to provide a more genetically defined classification.3 Both classifications omit mutated RUNX1 as a separate AML entity, as RUNX1 mutations are not specific enough to represent a distinct type of AML.