 Most GIST patients develop clinical resistance to KIT/PDGFRA tyrosine kinase inhibitors (TKI).     ///    and KIT/PDGFRA wild-type GISTs.     ///    "KIT kinase resistance mutations were not found in KIT/PDGFRA wild-type GISTs or in KIT-mutant GISTs showing unusual morphology and/or loss of KIT expression by IHC, indicating that resistance mechanisms are fundamentally different in these tumours. "