AIM:ToinvestigatethepositiverateandtypesofcellsthatexpressEpstein-Barrvirus-encodedsmallRNAs(EBERs)andtodeterminethedistributionofEBER-expressingcellsinidiopathicorbitalinflammatorypseudotumor(IOIP)tissues.METHODS:Weretrospectivelyexamined40archivedparaffinspecimensfromtwoteachinghospitalsinSouthernChinabetweenJanuary2007andJanuary2015thatwerepathologicallydeterminedtoexhibitIOIP.Elevenconcurrentparaffinspecimensofthyroid-associatedophthalmopathy(TAO)composedthecontrolgroup.InsituhybridizationwasperformedtodetectEBERs.ImmunohistochemistrywasemployedtodetectCD3,CD20,Vimentin,andsmoothmuscleactin(SMA),andthepositiverate,typesofpositivecells,anddistributionandlocationofEBERswereevaluated.RESULTS:ThepositiveexpressionrateofEBERswas47.5%(19/40)intheIOIPgroup,whichwassignificantlyhigherthanthatintheTAOgroup[0(0/11),P=0.011].IntheIOIPgroup,thelymphocyteinfiltrativesubtype,fibroticsubtype,andmixedsubtypeexhibitedEBER-positiveratesof57.1%(12/21),12.5%(1/8),and54.5%(6/11),respectively,andnosignificantdifferenceswerefoundbetweenthesesubtypes(P=0.085).PositivesignalsofEBERsweremainlypresentinmedium-smalllymphocytesbetweenoraroundfolliclesandinthenucleiofactivatedimmunoblasts(14/19).CONCLUSION:Thepositiverate,types,anddistributionofEBER-expressingcellsinIOIPhavebeendocumented.ThesefindingsareconduciveforabetterunderstandingoftheunderlyingmechanismsofEpstein-BarrvirusinfectioninIOIPpathogenesis.
