Gastrointestinal Stromal TumorsBenzamidesPiperazinesPyrimidinesProto-Oncogene Proteins c-kitGastrointestinal NeoplasmsAntineoplastic AgentsReceptor, Platelet-Derived Growth Factor alphaStromal CellsMesenchymomaNeoplasms, Connective TissueEpithelioid CellsMitotic IndexPyrrolesDuodenal NeoplasmsLeiomyosarcomaImmunohistochemistryIleal NeoplasmsJejunal NeoplasmsNeoplasms, Multiple PrimaryMutationIntestinal NeoplasmsTumor Markers, BiologicalIndolesSex Cord-Gonadal Stromal TumorsProtein Kinase InhibitorsStomach NeoplasmsTomography, X-Ray ComputedDigestive System Surgical ProceduresDNA Mutational AnalysisNeurofibromatosis 1SarcomaPrognosisCarney ComplexGastrectomyLeiomyomaTreatment OutcomeAntigens, CD34Drug Resistance, NeoplasmInterstitial Cells of Cajal