KIT mutations occur in approximately 80% of patients with gastrointestinal stromal tumors. The major region of KIT mutation in GIST is within exon 11, occurring in about 65% of patients. KIT exon 11 mutations are activating mutations and are typically sensitive to treatment with Imatinib.

KIT(cKIT) mutations are present in approximately 8-25% of cases of acute myeloid leukemia and have a higher prevalence in the favorable cytogenetic risk group including core binding factor (CBF) AMLs (ie, (t(8;21)(q22;q22)(RUNX1-RUNX1T1), inv(16)(p13q22)(CBFB-MYH11)) or normal karyotype AML. Mutations of KIT in AML are most common in KIT exon 17 (within the activation loop of the tyrosine kinase domain) but may also occur in KIT exons 8 (extracellular portion of the receptor implicated in dimerization), 9-11 (juxtamembrane/transmembrane domains). The presence of KIT mutations has been reported to be associated with a poorer survival and/or higher risk of relapse than expected for patients with the t(8;21)(q22;q22)(RUNX1-RUNX1T1), and to a lesser extent, in inv(16) AML. KIT mutations are also important in systemic mastocytosis and various mast cell disorders; over 90% of cases of systemic mastocytosis carry mutations in exon 17 of KIT (most commonly D816V or rarely D816H, D816Y or other variants). In patients with mastocytosis, the KIT mutations may be detectable in non-mast cell hematopoietic cells. The KIT D816V mutation has been shown to be resistant to imatinib; other KIT mutations may show variable responses to imatinib. The KIT D816V mutant has been reported to be sensitive to other tyrosine kinase inhibitors. In the context of core binding factor AMLs, the KIT mutation status can help direct therapeutic management.

Sunitinib