简介：AIM:Toclarifythecorrelationwithphenotypicexpression,clinicopathologicalfeatures,geneticalterationandmicrosatellite-instabilitystatusinsmallintestinaladenocarcinoma(SIA).METHODS:Thecasesof47patientsdiagnosedwithprimarySIAsthatweresurgicallyresectedatourinstitutionin1975-2005werestudied.Wereviewedclinicopathologicalfindings(age,gender,tumorsize,grossappearance,histologicalmorphologictype,invasiondepth,lymphaticpermeation,venousinvasion,andlymphnodemetastasis),andtheimmunohistochemicalexpressionofMUC5AC,MUC6,MUC2,CD10,andmismatch-repair(MMR)proteins(MLH1andMSH2).WeanalyzedKRASandBRAFgenemutations,andthemicrosatelliteinstability(MSI)status.TheimmunohistochemicalstainingofCD10,MUC2,MUC5ACandMUC6wasconsideredpositivewhendistinctstainingin>5%oftheadenocarcinomacellswasrecorded.ToevaluateofMMRproteinexpression,weusedadjacentnormaltissueincludinglymphoidfollicles,inflammatorycells,andstromalcellsasaninternalpositivecontrol.SectionswithoutnuclearstaininginthetumorcellswereconsideredtohavelosttheexpressionoftherespectiveMMRprotein.RESULTS:Therewere29malesand18femalespatients(meanage59.9years,range:23-87years).Tumorswerelocatedintheduodenumin14cases(30%),thejejunumin21cases(45%),andtheileumin12cases(25%).Aphenotypicexpressionanalysisrevealed20MUC2-positivetumors(42.6%),11MUC5AC-positive(23.4%),4MUC6-positive(8.5%),and7CD10-positive(14.9%).ThetumorsizesoftheMUC2(+)tumorsweresignificantlylargerthanthoseoftheMUC2(-)tumors(mean,5.7±1.4cmvs4.7±2.1cm,P<0.05).AllthreetumorswithadenomatouscomponentwerepositiveforMUC2(P<0.05).PolypoidappearancewasseensignificantlymorefrequentlyintheCD10(+)groupthanintheCD10(-)group(P<0.05).ThetumorsizewassignificantlylargerintheCD10(+)groupthanintheCD10(-)group(mean,5.9±1.4cmvs5.0±2.1cm,P<0.05).Of34SIAswithsuccessfullyobtainedMSIdata,4wereMSI-high.O