These forms were grouped as myeloproliferative diseases and were later considered myeloproliferative neoplasms by the 2016 WHO classification [3,4] and comprise different entities, such as BCR-ABL-positive chronic myeloid leukemia, chronic eosinophilic leukemia, mastocytosis, some myelodysplastic syndromes, and the three entities within BCR-ABL-negative chronic MPN, i.e., ET, PV and MF. The gene discussed is ABL1; the disease is mastocytosis.