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Introduction

HumanT-celllargegranularlymphocyte(LGL)leu-kemiaisaheterogeneousdisordercharacterizedbyaper-sistentincreaseinthenumberofperipheralbloodLGLswithfineorcoarseazurophilicgranules1.ThegranulescontainanumberofproteinsthatplayaroleincytolysissuchasperforinandgranzymeB1. αβT-cellreceptors(TCRs)areexpressedinmostcases,andthosewithγδTCRsareveryrare1,8.AfelineLGLlymphomaexpress-ingsurfaceCD3andperforinwasthoughttobeofT-cellorigin3.Althoughperforin-likeactivitywasnotobservedin6casesoffelineLGLneoplasm,2casesexpressedαβTCRs2.

Incattle,γδT-celllymphomaisaneoplasmchar-acterizedbypositivereactivityforWC1andperforin,andepitheliotropismisseeninmostcases4,7,11.Naturalkiller(NK)-likeT-celllymphomahasbeenreportedinacalf,andmanyneoplasticcellshadeosinophiliccytoplasmicgranulesthatwereofvariablesizeandpositiveforper-forin5.HerewereportacaseofhypergranularγδT-cell

lymphomainaheiferthatdidnotresemblethehumancounterpartatallandwasconsideredtobeacytologicvariantofγδT-celllymphoma.

Materials and methods

1. AnimalA 16-month-old Holstein heifer was examined

becauseofa3-dayhistoryofanorexia.Clinicalexami-nationrevealedemaciation,bilateralexophthalmoswithepiphora,andhyperthermia(41ºC).Despiteantimicrobialtreatment,theheifer’sconditionworsenedwithprogres-siveexophthalmos,anditwaseuthanizedoneweekafterthefirstexamination.

Atnecropsy, therewereseveral tumormassesupto5cmindiameteronthevulva,perineumandperianalarea.Oncutsection,theywerehomogeneous,whiteandfleshy.Theskinoftheuddershoweddiffuseswellingduetoneoplasticinvolvementofthedermisandsubcutis.Theocularmuscleswerealmostcompletelyreplacedbywhiteneoplastictissue,andtheglossalmuscleswereseverelyaffected.Thereweresparselydistributednodulesupto

Hypergranular γδ T-Cell Lymphoma in a Heifer

Kazumi NAITOU1, Yoshiharu ISHIKAWA2 and Koichi KADOTA2*1TobuLivestockHygieneServiceCenter,YamanashiPrefecture

(Fuefuki,Yamanashi406–0034,Japan)2HokkaidoResearchStation,NationalInstituteofAnimalHealth

(Toyohira,Sapporo062–0045,Japan)

AbstractLymphomawithlargegranularlymphocyte(LGL)morphologyinaheiferisdescribed.Themostnoticeablemacroscopicfindingwasneoplasticinvolvementoftheskin,mucosaeofthealimentarytract,urinarybladder,anduterus.Histologically,lymphomacellswithlargenumbersoffineeosinophilicgranulespredominatedintheneoplastictissue,andthegranuleswerepositiveforperforin.SurfaceCD3,CD5orWC1wasexpressedbysomeneoplasticcells.InadditiontotheepitheliotropismthatisafeatureofordinaryγδT-celllymphoma,theneoplasticcellsshowedangiodestructionanderythropha-gocytosis.ThesephenomenawerethoughttoresultfrommarkedactivationofneoplasticγδT-cells.ThepresentlymphomawasdistinctfromthepreviouslyreportedbovineNK-likeT-celllymphomainitstissuedistribution,cytomorphology,cytochemistry,andimmunophenotype.SincethislymphomawasregardedasacytologicvariantofγδT-celllymphoma,thetermhypergranularγδT-celllymphomaseemedtobemoreappropriatethanγδT-cellLGLlymphoma.

Discipline:AnimalhealthAdditional key words:angiodestructivegrowthpattern,largegranularlymphocytelymphoma,

perforin,WC1

JARQ41(1),79–83(2007)http://www.jircas.affrc.go.jp

*Correspondingauthor:e-mailkkadota@affrc.go.jpReceived17April2006;accepted30May2006.

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1.5cmindiameterintheobliquusinternusabdominisandglutealmuscles.Similarnoduleswerealsodetectedinsomeotherskeletalmuscles,andappearedtobegeneral-izedindistribution.

Thereweremultiple tumormasses,5to10cmindiameter,onthemucosalsurfaceoftherumen.Similarbutsmalleronesweredetectedinthereticulumandoma-sum,andthewalloftheabomasumwasdiffuselythick-ened.Variouslysizedtumormasseswerescatteredinthejejunumandileum,andthemajoritywereonthemucosalsurface.Scatteredtumormasseswerefoundontheserosaofthecolonandrectum.Nodules1to2cmindiameterwereoccasionallyseenintheliver.

Multiplenodules,0.5to1cmindiameter,werepres-entonthemucosalsurfaceoftheurinarybladder.Almostallpartsoftheuretericwallwerethickened.Frequently,themucosalsurfacesoftheoviduct,uterus,vagina,andvestibulumwere elevatedbyneoplasticproliferationsupto5cmindiameter.Somesmalleroneswerepresentontheserosalsurfaces.Mostpartsofbothovarieswerereplacedbyneoplastictissue.

Thesuperficial,abdominalandthoraciclymphnodeswereenlargedtovaryingdegrees.Thecapsuleofhepaticlymphnodeswasinfiltratedwithneoplastictissue,whichextended into theadjacentpancreatic tissue. The leftkidney,spleenandlunghadsingleneoplasticnodules.Numerousneoplasticfociwerepresent throughout theheart.Severaltumornodulesupto1cmindiameterwereadherenttotheduramatter.

2. Histology, immunohistochemistry and electron microscopy

Tissuesampleswerefixedin10%phosphate-buff-eredformalin,embeddedinparaffin,sectionedat4μm,andstainedwithhematoxylinandeosin(HE),Giemsa,phosphotungsticacidhematoxylin(PTAH)andnaphtholAS-Dchloroacetateesterase(CAE). Selectedparaffinsectionsweredewaxedandlabeledbytheavidin-biotin-peroxidasecomplex(ABC)method.Theprimaryantibod-iesusedwererabbitpolyclonalantibodiestoCD3ε(Dako,Glostrup, Denmark) and CD5 (Lab Vision, Fremont,CA,USA),andmousemonoclonalantibodiestoCD79a(Dako),CD57(BioGenexLaboratories,SanRamon,CA,USA)andWC1-N3(VeterinaryMedicalResearchandDevelopment,Pullman,WA,USA).Subsequentproce-dureswerecarriedoutbymeansofanimmunoperoxidaselabelingsystem(Nichirei,Tokyo,Japan).Smallpiecesfromformalin-fixedtissueswerepost-fixedin1%osmiumtetroxide,andembeddedinepoxyresin.Ultrathinsec-tionswerestainedwithuranylacetateandleadcitrate,andexaminedbyelectronmicroscopy(EM).

Results

Histologically,thereweredensediffusegrowthsoflymphomacellsinallofthenodularormassivelesionsexamined,butanangiocentricorangiodestructivegrowthpatternwasfoundsporadically(Fig.1A).Themostout-standingfindingwasepitheliotropism,andintraepithelialtumorcellscouldbeascertainedintheskin,rumen(Fig.1B),reticulum,omasum,abomasum,jejunum,ileum,uri-narybladder,uterus,andbronchiolarepithelium.Variousdegreesofneoplasticinvasionwereobservedinthelymphnodes,andtherewereneoplasticinfiltratesintheparacor-ticalzonesofpartiallyinvolvedlymphnodes.

Theneoplasticcellswere6to15µmindiameter,withapredominanceof largercells. Thenucleiwerevesicularandround,ovoidorirregular,withinconspicu-oustomedium-sizednucleoli.Thecytoplasmwasabun-dant,andmanyneoplasticcellscontainedfineeosino-philicgranules (Fig.1C). Incertainplaces,however,agranular lymphomacellsproliferatedpreponderantlyorexclusively(Fig.1D).ThegranulesstainedredwithGiemsa,andwerepositiveforPTAHbutnotforCAE.Afairnumberoftumorcellsshowederythrophagocytosis.Mitoticfigureswereplentiful.

Immunohistochemically, occasional neoplasticcellsstainedpositivelyforsurfaceCD3,CD5orWC1.NotumorcellsshowedpositivereactivityforCD57andCD79a. The intracytoplasmic granules were weaklypositiveforperforin(Fig.2A).Cytokeratinstaining,forwhichepithelialcellsstainedpositively,highlightedtheepitheliotropismoftheneoplasticcells(Fig.2B).

Ultrastructurally,themostcharacteristicfeatureofthelymphomacellswasthepresenceofelectron-densegranulesinthecytoplasm(Fig.3),thoughagranularcellswererarelyseen.Thegranulesvariedbetween0.1–0.8μmindiameter.Thegranulesizetendedtobelargerincellswithabundantgranules.Thereweremoderatequan-titiesofroughendoplasmicreticulum(RER)incellswithmanygranules,whereascellswithfewornogranuleswerecharacterizedbythepaucityoforganelles. Mostnucleiwereirregularincontour,havingabundanteuchro-matin.

Discussion

In thecasedescribedhere,manyneoplasticcellsthathadnumerouseosinophilicgranulesinthecytoplasmwere reminiscentofmastcellsormyelocytes,butdidnotshowmetachromasiaanddidnotstainwithperoxi-daseorCAE9,10.OnthebasisoftheexpressionofCD3,CD5,WC1,andperforinbyneoplasticcellsaswellastheabundanceofcytoplasmicgranules,apresumptive

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A B

Fig. 1. Histology of neoplastic lesions of the heiferA:Portahepatis.Twobloodvesselsareheavilyinvadedanddestroyedbyneoplasticcells.HE.×100.B:Rumen.Tumorcellsareisolatedoringroupswithintheepithe-lium.HE.×200.C:Jejunum.Almostalltumorcellshavenumerousacidophilicgranulesinthecytoplasm,whichareresponsiblefordisplacementofthenuclei.HE.×600.D:Jejunum.AlthoughthisisthesamelesionasinFig.1C,lymphomacellswithgranules(arrows)areinconspicuous.HE.×600.

Fig. 2. Immunohistochemistry of neoplastic lesions of the heiferA:Jejunum.Arrowsindicateneoplasticcellsthatareweaklypositiveforperforin.ABC.×1,000.B:Urinarybladder.Thetransitionalepitheliumisclearlyseenwithcytokeratin staining,whichhighlights theprominentepitheliotropism of cytokeratin-negative lymphomacells(arrows).ABC.×600.

A B

C D

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diagnosisofγδT-cellLGLlymphomawasmade1,4.Inhumans,themajorityofT-cellLGLneoplasmsareposi-tiveforαβTCRs,andcasesexpressingγδTCRsarerare1,8.Comparedwithhumancases,thecytoplasmicgranulesweremuchmoreprominentinthecurrentcase,andwerereadilydiscernibleinhistologicsections.Moreover,thislymphomawasquitedissimilarclinicopathologicallytothehumancounterpart,whichisachroniclymphoidleu-kemiaandhasanindolentclinicalcourse1.

Inthesinusoidsofthenormalratliver,LGLshavenumeroussmallcytoplasmicgranules,whereasperipheralbloodLGLscontainafewlargergranules12.ThehepaticLGLsareconsideredtobeaspecificpopulationofhighlyactivatedorfurtherdifferentiatedLGLs12.Withthisinmind,thepresentlymphomawithneoplasticcellshavingnumeroussmallgranuleswasinterpretableasaneoplasmofpredominantlyactivatedLGLs,andthehypergranularcellsmightbeintheultimatestageofγδT-cellactivation.ThiscasewascytologicallyandcytochemicallydistinctfromabovineNK-likeT-celllymphomawhosecompo-nentcellshadCAE-positivegranulesofvarioussizesandnumbers5.Inaddition,thelymphomashowedlittleten-dencytoformtumormassesandtheliverwasseverelyaffected5.

Although the number of cytotoxic granules wasmuchgreaterthaninordinaryγδT-celllymphomas11,thepresentneoplasmwasverysimilartosomeoftheselym-phomasinitstissuedistributionandepitheliotropism4,7.Theneoplasmwasregardedastheircytologicsubtype,andwasdesignatedhypergranularγδT-celllymphoma.AnangiodestructivegrowthpatternischaracteristicofhumanNK-cellneoplasms,butfocalvasodestructivepro-liferationmayalsobepresentinhumanγδT-celllympho-mas13.Thepresentneoplasmshowedasimilargrowthpatternandconsiderableerythrophagocytosis.Thefor-merhasnotbeenseeninbovineγδT-celllymphomas,butslighterythrophagiawasdetectedinameningealγδT-celllymphoma11.ThesephenomenainthepresentcasemaybeduetomarkedactivationofneoplasticγδT-cells;abundantcytotoxicgranulesarepresumablyassociatedwithdestructionofbloodvessels6.

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Fig. 3. Electron microscopy of tumor cellsUterus.Inhabitingthecytoplasmoflymphomacells,agreatnumberofelectron-densegranulesareconcentratedtoonesideofthecells.Onelymphomacellwithfewgranules(arrow)isalsovisible.EM.×6,000.

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