This data is reminiscent of reports on progression in other myeloid neoplasms such as MDS or MDS/MPN, and our previous reports on progression of SM to advSM or progression within advSM subtypes, e.g., to secondary mast cell leukemia, in which somatic mutations in NPM1, IDH2, or RUNX1 were also identified as late events and drivers for disease progression [29–35]. Here, NPM1 is linked to mast cell leukemia.