**7. Myelodysplastic/myeloproliferative neoplasm-unclassifiable (MDS/MPN-UC)**

MDS/MPN-UC is also called mixed myeloproliferative/myelodysplastic syndrome. Since it shows both MDS/MPN features and not meeting the criteria of the described MDS/MPN categories, this disorder is unclassifiable. A mutation on Jak2 kinase causing its constitutive activation might be involved in the disease at least in some MDS/MPN-UC patients. Adult patients with platelet-derived growth factor receptor gene rearrangements might be treated with imatinib mesylate.
