KIT and gastrointestinal stromal tumor: Imatinib mesylate (STI571) is a multi-kinase inhibitor approved for clinical use in the treatment of chronic myeloid leukemia, acute lymphoblastic leukemia (Philadelphia-positive), gastrointestinal stromal tumors (CD117-positive), and myeloid/lymphoid neoplasms with PDGFR gene rearrangements [133].