© 2015 Hong Kong College of Radiologists 27

Hong Kong J Radiol. 2015;18:27-36 | DOI: 10.12809/hkjr1414262

ORIGINAL ARTICLE CME

Correspondence: Prof YF Peng, Department of Radiology, Shanghai 10th People Hospital of Tongji University, Yanchang Road-301, Shanghai-200072, China; Shanghai Putuo Hospital of Traditional Chinese Medicine, Shanghai-200062, China.Email: peng2188@sina.com; mr_arunosome@yahoo.com

Submitted:26Aug2014;Accepted:7Nov2014.

Computed Tomography and Magnetic Resonance Imaging of Adenolymphoma (warthin’s Tumour) of the Parotid Gland

AK Yadav1, CC Xia1, YF Peng1,2, HD Shao1, XZ Gang1

1Department of Radiology, Shanghai 10th People’s Hospital of Tongji University, Shanghai, China; 2Department of Radiology, Shanghai Putuo Hospital of Traditional Chinese Medicine, Shanghai, China

ABSTRACTObjective: To characterise the computed tomography / magnetic resonance imaging (CT/MRI) features to diagnose adenolymphoma (Warthin’s tumour). Methods: Between February 2008 and December 2012, CT/MRI scans of consecutive patients referred for suspected parotid tumours were performed before surgery or fine-needle aspiration cytology. All patients underwent surgery and samples were sent for pathological confirmation of the diagnosis. Their CT/MRI scans with pathologically proven Warthin’s tumours were reviewed.Results: All of the 17 patients in the study were men, and aged between 43 and 86 years (mean, 65 years). All the patients initially presented with gradually increasing painless masses, with duration of symptoms ranging from 1 month to 120 months (mean, 61 months). Two patients were found to have bilateral Warthin’s tumour, nine had a left-sided Warthin’s tumour, and six had a right-sided Warthin’s tumour. Conclusion: The CT/MRI findings were helpful in distinguishing these benign lesions from other parotid gland tumours when biopsy results are non-diagnostic. Further studies are needed to assess the positive predictive value of the imaging features.

Key Words: Adenolymphoma; Magnetic resonance imaging; Tomography, X-ray computed

中文摘要

腮腺腺淋巴瘤（沃辛瘤）的電腦斷層掃描和磁共振成像（CT/MRI）

AK Yadav、夏琛琛、彭屹峰、邵鴻達、鋼熊炸

目的：介定腮腺腺淋巴瘤（沃辛瘤）的CT/MRI診斷特徵。

方法：2008年2月至2012年12月期間，所有腮腺腫瘤疑似病例均於術前或在細針穿刺抽吸活檢前作

CT/MRI檢查。所有病人均接受手術，其活檢樣本經病理學檢查，並回顧研究確診為腮腺沃辛瘤病例

的CT/MRI。結果：被納入研究的17例全為男性，年齡介乎43歲至86歲，平均65歲。所有患者初發症狀為體積逐

漸增大的無痛性腫塊，持續1至120個月（平均61個月）。其中2例雙側腮腺沃辛瘤，另9例左側腮腺

沃辛瘤，6例右側腮腺沃辛瘤。

Adenolymphoma of the Parotid Gland

28 Hong Kong J Radiol. 2015;18:27-36

INTRODUCTIONAdenolymphoma(Warthin’stumour)isabenigntumourof the salivarygland,which ispredominantly foundin theparotidgland.Warthin’s tumourwas initiallydescribed in1929andnamedafter thepathologistAldredScottWarthin.1 It is alsoknownaspapillarycystadenoma lymphomatosum, adenolymphoma,cystadenolymphoma,andpapillarycystadenoma. Itis a fairlycommon tumour, accounting for14% to30%ofparotid tumours, and iswell-knownamongotolaryngologists.Unlikebenignmixed tumours,Warthin’stumourrecursinlessthan2%ofpatientsandonly1%ofpatientsdevelopamalignanttumour.MoremendevelopWarthin’s tumourthanwomen,ataratioof5:1.2Warthin’stumourismostcommonlydiagnosedincidentallyoncomputed tomography (CT) scan.Thetumourusuallyoccurs inolderpatients,mostoften inthesixthandseventhdecadesoflife.3

Thereare severalhypothesesconcerningWarthin’stumour,but thewidelyacceptedexplanationdescribesit as a condition thatdevelops from thehyperplasiaof the salivaryduct cells isolated in the lymphnodeof theparotidglandduringembryogenesis.OthertheoriessuggestthatWarthin’stumouriscausedbytheinfiltrationof lymphocytes insideanexistingadenomaorinteractionofhyperplasiaofglandularepitheliumandexcessivelymphoidtissueinsidethestroma.4,5

Themost common presenta t ion i s tha t of anasymptomaticmass (81%)noted incidentallywhilewashingor shaving the face.Painand facialnervepalsyoccur lessfrequently.Whilepainfulmassesmaybeproducedbyobstructiveor inflammatorydisease, aclassicpainlessmassintheparotidglandisusuallyduetoaneoplasm,cyst,orlymphnode.6Localexcisionorsuperficialparotidectomy is establishedas the surgicalproceduresof choice.MostWarthin’s tumoursof theparotidglandare slow-growing,with smoothwell-definedmargins.

Preoperative imaginghasassumedamajor role insurgicalplanningforassessingthelocationofatumour.It isuseful tounderstand the typicalCT/magneticresonance imaging (MRI) features ofWarthin’stumour.Thepurposeofthisstudywastoassesspatients

suspected tohaveWarthin’s tumour todetect specificimaging findings toprovidemoreaccuratediagnosis.Imagingof theparotidglandshas twopurposes:first,to establish thepreciseextent and siteof anyparotidlesions;and,second,toprovidesomeindicationsofitspathologicalnature.Itisimportanttodeterminewhetheraparotidglandtumourisbenignormalignant.CTcouldidentifypatientswithpleomorphicadenomas,Warthin’stumours,ormalignanttumours,andevaluatetheextentof anyparotidgland tumours.Moreover,detailedinformationon signal intensityandwashout ratio inaparotidgland tumourbycontrast-enhancedMRIhasbeen reported forpleomorphicadenomas,Warthin’stumours,andmalignant tumours.HenceCT/MRIwithhistopathologygivespromisingresultsfordiagnosisofWarthin’stumour.

METHODSPatients BetweenFebruary2008andDecember2012,CTandMRIscansofconsecutivepatientsreferredforsuspectedparotidtumourswereperformedbeforesurgeryorfine-needleaspirationcytology.Allpatientsunderwentsurgery and sampleswere sent for pathologicalconfirmationofthediagnosis.TheCT/MRIscansofallpatientswithpathologicallyprovenWarthin’s tumourswere reviewed.This studywasapprovedby the localethicscommittee.

Imaging Techniques and Image AnalysisA4-sliceCTunit (GEHealthcare,Wauwatosa [WI],USA) and 3.0 TMRI unit (Siemens, Erlangen,Germany)withaneckcoilwereused.TheCTimageswerereconstructedat3-to5-mmthicknessinboththeaxial andcoronalplanes.The section thicknessandpitchfactorwere in the rangesof3 to5mmand1or<1, respectively. Imageswereacquiredat120kVand200mA,withatotalscanningtimeof35seconds.Anintravenousbolusdoseof70mlofnon-ioniccontrast(iohexol,350mgI/ml)wasadministered topatientsataninjectionrateof2.5ml/s.

TheMRIexaminationincludedmultiplanarimages.TheminimumsequencesareshowninTable1.Twoboard-certifiedradiologists (sub-specialised inheadandneckradiology)evaluated theCT/MRI scansaccording to

結論：如未能根據活檢結果作出診斷時，CT/MRI能將此類良性病變與其他腮腺腫瘤區分開來。但須

進一步研究這些影像學特徵對沃辛瘤的陽性預測值。

AK Yadav, CC Xia, YF Peng, et al

Hong Kong J Radiol. 2015;18:27-36 29

thetumourlocation,size,margins,contour,attenuationand signal intensity, andenhancementpattern.Thelesionmargins(well-definedorill-defined),size(long-and short-axisdiametersmeasuredonaxial images),location (superficialordeep), andcontour (smoothorlobulated)wererecorded.Avirtuallinewasdrawnfromthelateralborderoftheposteriorbellyofthedigastricmusclesandretromandibularveintothelateraledgeofthemandible to locate the superficial anddeep lobes.7 TheCTattenuationwascomparedwith thatof theadjoiningskeletalmusclesandtissues.

SignalonT1-weightedimageswasjudgedaslow(iso-to-lowsignalorhypointensity)when the signalof theparotidglandwasequalor lower than the signalofmuscle,high (high signalorhyperintense)when thesignalwasbrighter thanmuscle, and strong (highlyhyperintense)when the signalwascloser to thatofwater(cerebrospinalfluid)thanthatoftheparotidgland.T2-weightedand turbo-inversion recoverymagnitudecharacteristicswere reportedas low (hypointense)when the signalof the tumourwas lower than thatofparotidtissue,high(hyperintense)whenthesignalwasequal toorbrighter than thatofnormalparotid tissue,and strong (highlyhyperintense)when the signalwascloser to thatofwater (cerebrospinal fluid) than thatofparotid tissue.The tumour texturewas recordedasheterogeneousorhomogeneous inattenuationandhigh-signal intensity.OnMRI, the tumour texturewasbasedontheappearanceofthelesionsonT2-weightedimaging.Appearancewasclassifiedas lobulatedandcystic /necroticwithareaswithout enhancement.Theapproximate tumourvolumewascalculatedbyusing theproductof tumour length,width, anddepth.Furthermore,thetumourappearancewasclassifiedintohomogeneousandheterogeneous,andobviousandnon-obviousonbothpre-andpost-contrastsequences.

RESULTSAll17patientsweremen,andagedbetween43and

86years (mean,65years).All thepatients initiallypresentedwithgradually increasingpainlessmasses,withadurationof symptoms ranging from1month to120months(mean,61months).TwopatientswerefoundtohavebilateralWarthin’s tumour,ninehad left-sidedWarthin’s tumour,andsixhad right-sidedWarthin’stumour.Nopatientshadmultiple lesions.Theparotidglandwasgroupedintodeepandsuperficiallobes,whichwereboundedwiththelinelinkingtheretromandibularveinandinnersternocleidomastoidastheboundary,andtheupperandlowerpoleswereboundwiththeearlobe.Theclinicalprofile,imagingfindings,andfinaldiagnosisofWarthin̓stumourareshowninTable2.

LocationThe tumourswere located in the parotid spacecontaining the facialnerve, retromandibularvein,external carotidartery, and intraparotid lymphnode.Tentumourswerelocatedatthesuperficiallobe(5left-sided,3 right-sided, and2werebilateral [Figure1])andsevenwereinthedeeplobeoftheparotidgland(4left-sidedand3right-sided,withnobilateraldeeplobetumours).

Shape, Size, and NumbersAllofthetumourshadsharpwell-definedmargins,andwerewithoval-to-round shape.Eleven tumourshadsmoothmargins,onewascystic, threewere lobulated,threewereboth solidandcystic.Themean long-axisdiameterwas2.34cm (range,1.20-3.40cm), and theaverageshort-axisdiameterwas2.88cm(range,1.20-6.00cm).

Texture and EnhancementOnplainCT, three tumourswerehyperdensewithheterogeneity, amongwhichonehadhaemorrhagicnecrosis (20HU) [Figure2].OnCTwithcontrast,seven tumourswerehyperdensewithhomogeneity,amongwhichonewas found tobehyperdensewithheterogeneity.OnepatienthadbothCTandMRI

Axial T1-weighted Axial T2-weighted Coronal T2-weighted Axial gadolinium-enhanced T1-weighted

Repetition time (ms) 650 4540 4540 802Echo time (ms) 10 90 96 10Section thickness (mm) 4 4 4 4Field of view (mm) 230 230 220 230Resolution (matrix) 320 x 224 320 x 237 320 x 256 320 x 224Voxel size (mm) 1.0 x 0.7 x 4.0 0.9 x 0.7 x 4.0 0.9 x 0.7 x 4.0 1.0 x 0.7 x 4.0

Table 1. Specifications of multiplanar images.

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30 Hong Kong J Radiol. 2015;18:27-36

Pa-tient No.

Age (years) /

sex

Modality CT or MRI

Tumour CT enhancement (HU)AP: 25 secondsDP: 60 seconds

V (max FOV) / MRI enhancement

Diagnosis (histopathology)

Location Size (cm) Margin Contour

1 43 / M CT+C Superficial; left

2.5 x 3.0 x 4.0 Well-defined Lobulated, uniform hyperdensity

Obvious uniform enhancementV 45,VP V 70,DP V 65

Adenolymphoma

2 66 / M CT+C Superficial; left

2.9 x 2.5 x 3.0 Well-defined Smooth, solid and cystic, heterogeneous hyperdensity

Obvious uniform enhancement (solid part)V 45, VP V 80, DP V 66

Adenolymphoma

3 58 / M CT+C Deep; left 2.5 x 2.5 x 3.5 Well-defined Smooth, cystic with wall nodularity

Nodule has obvious enhancementV 30, VP V 60, DP V 45

Adenolymphoma

4 56 / M CT+C Superficial; bilateral

Left: 2.0 x 2.0 x 2.6Right: 2.0 x 2.1 x 3.0

Well-defined Smooth, homogeneous high density

Obvious enhancementV 45, VP V 90, DP V 75

Adenolymphoma

5 73 / M CT+C Superficial; left

2.2 x 2.5 x 3.5 Well-defined Lobulated, uniform high density

Obvious enhancementV 38, VP V 75, DP V 68

Adenolymphoma

6 58 / M CT+C Superficial; bilateral

Left: 2.0 x 1.5 x 3.5Right: 1.2 x 0.8 x 1.5

Well-defined Smooth, uniform high density Obvious enhancementV 35, VP V 65, DP V 56

Adenolymphoma

7 73 / M CT+C Deep; left 1.8 x 2.0 x 2.5 Well-defined Smooth, homogeneous high density

Obvious enhancementV 40, VP V 75, DP V 65

Adenolymphoma

8 73 / M CT+C Superficial; right

1.6 x1.5 x2.5 Well-defined Smooth, homogeneous iso-to-high density

Obvious enhancementV 35, VP V 75, DP V 55

Adenolymphoma

9 76 / M MRI+C Superficial; right

1.6 x 1.5 x 1.8 Well-defined Smooth, homogeneous iso signal on T1-weighted and high signal on T2-weighted

Obvious and uniform enhancementFast in and fast out

Adenolymphoma

10 61 / M MRI+C Superficial; left

1.6 x 1.5 x 2.6 Well-defined Smooth, homogeneous low signal on T1-weighted and high signal on T2-weighted

Obvious and uniform enhancementFast in and fast out

Adenolymphoma

11 62 / M MRI+C Deep; right 3.3 x 3.0 x 3.5 Well-defined Smooth, solid and cystic, low-to-iso signal on T1-weighted and non-homogeneous high signal on T2-weighted

Solid part well-enhanced Adenolymphoma

12 62 / M MRI+C Deep; right 3.4 x 3.0 x 3.5 Well-defined Smooth, solid and cystic, iso signal on T1-weighted and non-homogeneous high signal on T2-weighted

Solid part obvious enhancement

Adenolymphoma

13 68 / M MRI+C Deep; right 1.5 x 1.7 x 2.5 Well-defined Smooth, slight high signal on T1-weighted and homogeneous high signal on T2-weighted

Obvious homogeneous enhancement

Adenolymphoma

14 54 / M MRI+C and CT

Superficial; left

3.2 x 2.5 x 3.5 Well-defined Lobulated, cystic non-homogeneous slight high signal on T1-weighted and non-homogeneous high signal on T2-weighted

Solid part obvious enhancementV 45

Adenolymphoma

15 55 / M CT Superficial; right

1.2 x 1.3 x 2.0 Well-defined Heterogeneous hyperdensity V 40 Adenolymphoma

16 72 / M CT Deep; left 3.5 x 3.0 x 6.0 Well-defined Necrosis and haemorrhage in lesion, heterogeneous hyperdensity

V 40Necrosis V 20

Adenolymphoma

17 86 / M CT Deep; left 3.0 x 2.6 x 3.0 Well-defined Heterogeneous hyperdensity with calcification

V 40 Adenolymphoma

Table 2. Clinical profile, imaging findings, and final diagnosis of patients with parotid tumour.

Abbreviations: AP = arterial phase; CT/MRI = computed tomography/magnetic resonance imaging; CT+C = computed tomography with contrast; DP = delayed phase; FOV = field of view; MRI+C = magnetic resonance imaging with contrast; V = CT attenuation value; VP = venous phase.

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showingcystic, lobulated tumourwithhigh intensityand hyperdensity (Figure 3).Most ofCT scansshowed smooth, solid, cystic, lobulated tumourswithwell-definedmargins.Onepatientdemonstrated

hyperdensity,heterogeneouswithcalcificationonplainCT.Among fiveMRIpatients all showedsmooth,homogeneous intensity; theT1-weightedMRI showediso-to-lowsignalswhereashigh signalwas shownonT2-weighted images (Figure 4).Gadoliniumenhancementwasmarked,buthomogeneous.

Allpatients in this studyunderwent surgery, eitherpartial or total parotidectomydepending on thelocationof the tumours, anda samplewas sent forhistopathologydiagnosis.Noclinicalevidenceoflocaltumourrecurrencehasbeendetected.

DISCUSSIONParotidisaGreekwordthatmeans‘neartheear’.Theparotidglandsare the largestof the salivaryglands.Theyarepairedglands that containmucusand serouscells,andaductalnetwork.Aparotidmassisacommonclinicalpresentation inheadandneck imaging. Inadults,benigntumourssuchaspleomorphicadenomaorWarthin’stumourarethemostcommondiagnoses.8Inthepast,Warthin’stumourwasseenprimarilyinwhitemen,butitisbecomingmoreprevalentbothinAfricanAmericansandinwomen.AlthoughWarthin’stumourcanoccurelsewhere,itismostcommonlyfoundintheparotidgland.Inoneseries,alloftheWarthin’stumourswerelocatedintheparotidgland.9Anotherseriesfound90%ofWarthin’s tumourswithin theparotidgland,7.6% in thecervical lymphnodes, and2.3% in thesubmandibulargland.10

Figure 1. Computed tomography images of a 56-year-old man (patient No. 4) with bilateral neck mass for 10 years: (a) plain axial view shows bilateral homogeneous masses with well-defined margins located superficially (arrows) and (b) view with contrast shows bilateral homogeneous tumours with obvious enhancement (arrows).

(a) (b)

Figure 2. A computed tomography image of a 72-year-old man (patient No. 16) with a left-sided neck mass: axial view shows a deep lobe heterogeneous parotid lesion with well-defined margins, with high density (haemorrhage) and low density (necrosis/cyst: 3.5 x 3.0 x 6.0 cm) inside the tumour (arrow).

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Warthin’s tumour is themost frequentmonomorphicadenomaof themajor salivaryglands.Clinically,Warthin’s tumourappears as a slow-growing tumour,which isoften fluctuantonpalpationdue to its cysticnature.Warthin’s tumour is the secondmost commonbenignparotidglandneoplasm inadults andchildren.This tumour is themost commonneoplasm thatmanifests asmultiple lesions, and isbilateral inup to10%ofcases.Themost acceptedhypothesis abouttheoriginofWarthin’s tumour is that it developsfromsalivaryduct inclusions in the lymphnodesafterembryonicdevelopmentof theparotidgland.11Benign

tumourshaveonlyrarelybeenassociatedwithcigarettesmoking,which focusesattentionon thenatureof theunderlyingneoplasticprocessandhow itmaydifferfromotherbenigntumoursbut,accordingtoKotwall,12 smokershave8timestheriskofdevelopingWarthin’stumour.Althoughgenerallybelievedtobeanadenoma,Allegra13 suggested thatWarthin’s tumourmaybeadelayedhypersensitivityreaction.

Warthin’stumourisanadenomawithavariablenumberof cysts filledwithmucoidorbrown fluid.Thecystsarelinedwithpapillaryproliferationsofdouble-layered

(a)

(d) (e) (f)

(b) (c)

Figure 3. Computed tomography (CT) and magnetic resonance (MR) images of a 54-year-old man (patient No. 14) with a left-sided neck mass: (a) plain axial CT image shows a superficial lobe left-sided mass with well-defined margins (arrow), with isodensity, (b) Coronal T2-weighted MR image shows iso-to-high signal (arrow), (c) Coronal post-contrast T1-weighted MR image shows obvious enhancement of the heterogeneous mass (arrow), (d) axial T1-weighted MR image shows iso-to-high signal with haemorrhagic mass (3.2 x 2.5 x 3.5) [arrow], (e) axial T1-weighted fat-saturated MR image shows high signal mass (arrow) with a small low signal lesion inside suggestive of old haemorrhage (arrow), and (f) axial post-contrast T1-weighted MR image shows obvious enhancement of the superficial lobe heterogeneous mass with clear margins (arrow).

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oncocyticepitheliumandsupportingstromacomposedofgreatamountsoffollicle-containinglymphoidtissue(Figure5).The tumouroccasionallycontains focalhaemorrhageandnecrosis.Parotidectomy is themostwidelyaccepted surgical treatment forparotid tumourremoval.14Themost seriouscomplicationsof surgicaltreatment include facialnervedysfunction,Frey’ssyndrome,andlocalrecurrences.

CTandMRIdepictthemass,andthefindingsmaybediagnostic inroutinecaseswith typical features.CTisthemethodof choice for imagingpatients suspectedtohave inflammatorydisease (abscess, calculi,majorsalivaryductdilation,or acute inflammation)or forpatientswitha contraindication forMRI.ForCTimaging,bothpre- andpost-contrast studiesmustbeperformed inorder todetect calcification (Figure6).15 MRIisthemethodofchoiceforimagingpatientswith

palpablemasses forwhom there is a strong suspicionthat the lesion isneoplastic.MRIgives informationon theexact localisationandextentof the lesionsandaddressesneighbouring structures.Ultrasound (US)is auseful technique toassess superficialparotid,submandibular, and sublingualmasses.US,however,showsa lackof specificity for cystic lesionsanddeeplobeevaluation,andtherelationshipofatumourtothefacialnerve isdifficult for surgeons toappreciateonUS images.16,17Ultrasoundhasbeenable to identifyaWarthin’stumourbasedonechostructure,margins,andvascularity.18,19CThelps in identifying the structure,margins,numberof lesions,patternof enhancement,washout timeframes, andattenuationcoefficients todifferentiatebetweenvariousparotid lesions.3OnCTandMRI,Warthin’s tumour typicallyappearswell-circumscribedwithhomogeneous, cystic,or solidlesions in theparotidorperiparotid region,most

Figure 4. Magnetic resonance images of a 61-year-old man (patient No. 10) with Warthin’s tumour with no specific clinical manifestations: (a) axial T1-weighted turbospin-echo image shows a left posterior homogeneous parotid gland mass with iso-low signal with clear margins (arrow), (b) axial T2-weighted turbospin-echo image shows a left parotid gland mass with clear margins and high signal lesion (arrow), (c) coronal T2-weighted turbospin-echo image shows a left parotid gland tumour with slight high signal with clear margins (arrow), and (d) axial post-contrast T1-weighted image shows a left superficial lobe parotid gland tumour with high intensity signal with clear margins (arrow).

(a)

(c) (d)

(b)

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Figure 5. Histopathology of a parotid mass: (a) surface epithelium consists of a double layer, the top layer of tall columnar oncocytic cells (arrowhead) and a basal layer of polygonal cells (arrow) [H&E; original magnification, x 400]. (b) Tumour is multifocal and bilateral with the same frequency. Note the tall columnar cells (arrowhead) enclosing the lymphoid stroma (arrow) [H&E; original magnification, x 100].

commonlyinvolvingtheinferiorpoleofthegland.TheappearanceofmultipleorbilateralparotidorperiparotidmassesissuggestiveofaWarthin’stumour.

AlthoughMRI ismorecommonlyused toevaluateparotidmasses,CT imaginghasalso shownpromiseinelucidatingparotidmasses.MRI is anestablishedwayofshowingthemorphologyandextentofheadandneck tumoursand their adjacent structures.However,it is commonly thought thatMRI cannotmake areliabledistinctionbetweenbenignandmalignant

neoplasms.The importantdifferentialdiagnoses forwell-definedenhancingparotid tumours seenonCTincludeWarthin’s tumourandbasal cell adenoma.Warthin’stumourshowsenhancementintheearlypost-contrast scanphase,butdecreasedenhancement in thedelayedphase.20On thebasisofBryanet al’s study,21 CTdonewithahigh-resolutionCTscanneristheinitialradiographicprocedureofchoiceforevaluatingsalivaryglandmasses,particularly ifneoplasm is theprimaryconsideration.ForWarthin’s tumour,89%of foci areenhancedmarkedly in theearly stageanddecreaseindensity in the late stage (120 seconds), therefore,delayedenhancement isnot seen.Amalignantparotidtumourshowsirregularappearance,easyhaemorrhage,necrosis andcrystallisation, and infiltrativegrowth.Amalignantparotid tumour is apt to induce injuryofthe facialnerve, facialparalysis, and regionalnodalmetastasis.22TheparotidWarthin’stumourinallofthepatientsinthisstudyhadsharpwell-definedmargins.

Warthin’s tumoursareusuallydiagnosed inelderlymen,with10% to15%having synchronousbilateraldisease.20There is anoverlapof radiologic featuresbetweenWarthin’s tumourandotherbenign tumourssuchasoncocytomaandbasal cell adenomaand,toa lesserdegree,pleomorphicadenoma.BenignparotidWarthin’s tumourusuallyoccurs in the sixthdecadeof life andmainly inmen,whopresentwithCTorMRI findingsofwell-definedmargins, solid,cystic, lobulated,well-circumscribed,homogeneouslesions (Figure7).These findingsareatypical forpleomorphicadenoma.AstudybyChoi et al23 found

(a) (b)

Figure 6. An axial computed tomography image of an 86-year-old man (patient No. 17) with a left-sided deep lobe parotid mass shows well-defined margins with a calcified lesion (arrow).

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Figure 7. Computed tomography images of a 58-year-old man (patient No. 3) with a left-sided deep lobe parotid mass. (a) An axial image shows the mass with clear margins (arrow) and (b) with iso-density indicating a cystic lesion (arrow) [15 HU: 2.5 x 2.5 x 3.5 cm].

(a) (b)

thatWarthin’stumour(8outof9)showedstrongearlyphaseenhancementwithadecrease inattenuationondelayedimaging(120seconds)asopposedtothesignsforpleomorphicadenoma(30outof35)whichshowedincreaseddelayedenhancement.3A30%washoutratiothresholdcanbeuseful forpredictingwhetherparotidgland tumoursarebenignormalignant.Warthin’stumourstypicallydemonstrate≥30%washout,whereasmalignant tumoursdemonstrate lowwashoutof<30%andcomplicatedcysts showearlyenhancementandlowwashout ratio (≤30%). Ikedaat al24 had similarfindingswith44.0%(standarddeviation [SD],20.4%)averagewashout ratioofWarthin’s tumourcomparedwithmalignant tumours,whichhadawashout ratioof11.9%(SD,11.6%).According toSakamotoet al,25 a heavyT2-weighted sequencecanhelp todistinguishapleomorphicadenoma (whichusuallyappearsmoreheterogeneous) fromaWarthin’s tumour (whichusuallyappearsmorehomogeneous).Theprotocol forMRIofparotidgland lesionsconsistsof four imagingsequences inaddition to sagittal localising images.Themost important imagesareaxialT2-weightedimagesandaxial andcoronal contrast-enhanced fat-suppressed images.Toobtainoptimaldelineationof atumour,weuse3-mmsectionsthroughthegland,withagapof0.5mmor1.0mmbetween sections.26Thisallowsevaluationofthetumourmarginsaswellasthe

relationshipofthetumourtotheramusofthemandible,musclesofmastication,andretromandibularvein.

CONCLUSIONSFormiddle-agedoroldermenwithasmokinghistory,iftheyhavepainlessfociinthesuperioranddeeppartsoftheparotidglandshowingaclearboundary,significantenhancement, anduniformornon-uniformdensity / signalwithmoderateor significant enhancement,especially forunilateralorbilateral foci, parotidWarthin’s tumour shouldbeconsidered.Warthin’stumourpresents as a lymphocytic infiltrate andcysticepithelialproliferation.Thecysts are linedwithadouble layerof characteristic eosinophilic epithelialcells (oncocytes) andembeddedonadense lymphoidstroma.Smokers have a high risk of developingWarthin’s tumour.OnplainCT,Warthin’s tumoursshowhyperdensityandareheterogeneousinnaturewithhigh-densityhaemorrhageand low-densitynecrosisorcyst.OnCTwithcontrast,Warthin’s tumours showhighhyperdensitywithobviousenhancement.OnMRI,Warthin’stumoursshowiso-lowsignalonT1-weightedimages,buthighsignalonT2-weightedandgadolinium-enhanced imagesandarehomogeneous innature.CTis themethodof choice forpatientswith suspectedinflammatorydiseaseand forpatients contraindicatedforMRI,whereasMRI is themethodof choice for

Adenolymphoma of the Parotid Gland

36 Hong Kong J Radiol. 2015;18:27-36

patientswithpalpablemassesandstrongsuspicionthatthe lesion is aneoplasm.Ourextensive routineMRIstudy requires approximately15minutes toobtainallthe imagesand is excellentnotonly for assessing theextentof a salivarygland tumourand the relationshipto theadjacent structures,but also fordeterminingwhetherthetumourisbenignormalignant.MRIgivesinformationon theexact localisationandextentof thelesionsandaddressesneighbouringstructures,henceCTorMRIwithapathologyprovidesaccuratediagnosis.Conservativeparotidectomyisthemostwidelyacceptedsurgicaltreatmentforparotidtumourremoval.

DECLARATIONNoconflictsofinterestsweredeclaredbyauthors.

ACKNOwLEDGEMENTWiththankstotheShanghai10thPeople’sHospitalofTongjiUniversity,Shanghai,China.

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