正常胸腺及胸腺病變的CT表現(xiàn) 呂曉飛課件

正常胸腺及胸腺病變

—CT表現(xiàn)

TheNormalandAbnormalThymus

——CTimagingfinding南方醫(yī)院影像中心2009級(jí)博士研究生呂曉飛Content胸腺病變的CT表現(xiàn)3正常胸腺的CT表現(xiàn)2概述1胸腺是一種復(fù)雜的淋巴上皮器官，具有調(diào)節(jié)細(xì)胞免疫的功能，在人類正常免疫中是不可缺少的。CT及MR在胸腺異常的診斷中有重要作用，有利于評(píng)價(jià)是否正常及胸腺病變的范圍。概述1胎兒第6周，胸腺起源于第三及第四咽囊；第7周，胸腺始基延長(zhǎng)并呈圓柱狀形態(tài)，形成胸腺咽管，逐漸移行至前縱隔；第8周，胸腺始基于下極融合；第10周，肝臟組織及骨髓內(nèi)的小淋巴樣細(xì)胞移行至胸腺始基；第14~16周，胸腺進(jìn)一步分化形成皮質(zhì)及髓質(zhì)成分。胚胎發(fā)育正常胸腺解剖位置

位于前上縱隔，上達(dá)胸廓入口（甚至突入頸部接近甲狀腺下緣），下至心包前面上部，兩側(cè)臨近縱隔胸膜，后面貼附心包及左頭臂靜脈及主動(dòng)脈弓。胸腺的位置上界不超過(guò)胸骨柄上緣，下緣不超過(guò)左心室上緣或主動(dòng)脈根部層面，外緣不超過(guò)上腔靜脈、主動(dòng)彌弓外緣．其前緣位置正?？呻S周圍結(jié)構(gòu)改變而向左或向右移位。正常胸腺解剖AB異位胸腺Ectopicandaccessorythymictissuemayoccuranywherealongthepathofdescent(thymopharyngealduct)astheresultoffailureofdescent,sequestration,orfailuretoinvolute.Ectopicoraccessorythymictissuemaybefoundinthevicinityofthesuperiorvenacava,brachiocephalicvessels,andaorta.Rarely,itmaybefoundintheposteriormediastinumoreveninthedermis.異位胸腺Figure2.Cervicalcomponentofthethymusina3-year-oldboywithastrongmaternalfamilyhistoryofpapillarythyroidcarcinoma.Thecervicalcomponentwasmisinterpretedasan“exophytictumorofthethyroidgland.”Contrast-enhancedCTscansshowanormalmediastinalthymus(arrowsinA)anditscervicalcomponent(arrowsinB).Follow-upstudies2yearslatershowednochange,andthepatientremainedasymptomatic.AB正常CT表現(xiàn)（形態(tài)）9歲以下多呈方形或梯形，10歲以后隨年齡變化較大。正常CT表現(xiàn)（密度）在6-19歲人群中胸腺的CT密度與肌肉相同或稍高，CT值約為30Hu。由于隨年齡增加腺體遂漸消失而代之以脂肪，故從青春期至25歲期間，以前外凸的外緣變得扁平或內(nèi)陷，CT值比肌肉低。25歲后胸腺進(jìn)一步萎縮，不再能見(jiàn)到明確的軟組織密度的胸腺結(jié)構(gòu)，但可見(jiàn)在較豐富的脂肪背景上軟組織密度島，萎縮的速度和程度因人而異。在83%的小于50歲的人群中還可見(jiàn)正常胸腺。此后前縱隔完全脂肪化，但大部分人還可見(jiàn)到密度稍高于脂肪的殘存的纖維性胸腺框架。NORMALorABNORMAL??Onthebasisofthisreview,wehavedrawnthefollowingconclusionsregardingtheappearanceofthethymusglandandthedetectionofthymicabnormalities:Thethymusglandislargestatpuberty,anditsoverallsizedoesnotchangesignificantlywithage.Itoccupiesessentiallyallofthemediastinalcompartmentanteriortotheaorticarch,superiorvenacava,andgreatvesselsthroughoutlife.2.Afterpuberty,parenchymalatrophywithintheglandoccurs,withthegreatestpercentageofparenchymalreplacementbyfatoccurringbetweentheagesof31and40.3.Afterage40,thepresenceofasphericalorovalfocalsoft-tissuemasswithinthethymusglandusuallyrepresentaneoplasm.4.Beforeage40,differentiationofasmallthymomafromnormalresidualthymic

parenchymaltissuemaybeimpossibleonthebasisofsizealone.5.Atallages,athymomausuallyproducesafocalbulgeinthenormallysmoothadjacentvisceral-pleuralsurface.Moore,A.V.,etal.,Age-relatedchangesinthethymusgland:CT-pathologiccorrelation.AJRAmJRoentgenol,1983.141(2):p.241-6.（二）腫瘤病變（一）非腫瘤病變1.胸腺增生2.胸腺淋巴樣（濾泡性）增生3.胸腺囊腫1.胸腺上皮細(xì)胞腫瘤：胸腺瘤2.胸腺非上皮性腫瘤（1）胸腺淋巴瘤（2）胸腺類癌（3）胸腺脂肪瘤（4）縱隔生殖細(xì)胞瘤胸腺病變的CT表現(xiàn)31.胸腺增生

胸腺真性增生的定義是胸腺變大，但是組織結(jié)構(gòu)維持正常的，只是大小超過(guò)同一年齡段正常的上限，不涉及任何病理性質(zhì)的胸腺改變。胸腺真性增生常常見(jiàn)于機(jī)體遇到各種應(yīng)激事件，免疫處于較大的挑戰(zhàn)時(shí)期，比如腫瘤的化療、放療，皮質(zhì)醇激素治療，燒傷等應(yīng)激事件，以后部分患者可恢復(fù)到正常大小。常合并內(nèi)分泌異常，如特發(fā)性甲狀腺腫、格雷?。谞钕僦卸荆┖椭朔蚀蟀Y。胸腺?gòu)浡栽龃螅跃S持正常形態(tài)，兩緣對(duì)稱，呈光滑的不分葉的外形，CT值與正常者相似。（一）非腫瘤病變Case2胸腺真性增生，14歲，男。原發(fā)性T細(xì)胞淋巴瘤化療后。Case1胸腺真性增生，29歲，女性患者，合并Grave’s病。A.

胸腺體積輕度增大，邊緣略膨隆。B。經(jīng)治療3年后，胸腺體積縮小如正常。36歲，女性患者。胸腺淋巴樣（濾泡性）增生，胸輕度增大，邊緣稍隆起。3.胸腺囊腫胸腺囊腫不多見(jiàn)，占前縱隔腫瘤1%-3%?？蔀橄忍旎蚝筇飓@得性，根據(jù)病理組織學(xué)將胸腺囊腫分為三類：（1）先天性胸腺囊腫，可發(fā)生于胚胎期胸腺移行途中頸部至縱隔的任何部位，但最常見(jiàn)于前上縱隔胸腺區(qū)。頸部胸腺囊腫最常見(jiàn)于3-8歲兒童，縱隔胸腺囊腫多見(jiàn)于成人。多無(wú)癥狀，偶在查體或因囊腫大有壓迫癥狀，如胸悶不適、胸痛行X線檢查時(shí)被發(fā)現(xiàn)。（2）獲得性胸腺囊腫，常見(jiàn)原因?yàn)楦腥?，但也有認(rèn)為Hassall氏小體擴(kuò)張構(gòu)成，好發(fā)于無(wú)癥狀的男性。有報(bào)道在免疫缺陷病毒感染的無(wú)癥狀的患者中可發(fā)生巨大的多房性囊腫。（3）囊性胸腺腫瘤，此系胸腺腫瘤囊性變。一些胸腺腫瘤，如：何杰金氏病、精原細(xì)胞瘤、胸腺癌也可表現(xiàn)為廣泛的囊性改變，甚至掩蓋了原來(lái)的腫瘤，但后者從未見(jiàn)有完全囊變而形成薄壁囊腫者。3.胸腺囊腫ABCASE1Thymiccystina66-year-oldwoman.

(A)Contrast-enhancedCTscanshowsanincidentallynotedanteriormediastinallesion(arrow)withwell-circumscribedbordersandsoft-tissueattenuation.Thelesionisindistinguishablefromasolidmass.(B)OnaT2-weightedMRimage,thelesion(arrow)ishyperintenseandcontainsafluidlevel,findingsthatindicateahemorrhagicormucin-containingcysticlesion.Thelesionwassurgicallyremoved,andpathologicanalysisdemonstratedathymiccyst.3.胸腺囊腫CASE2Thymiccystassociatedwithinfection

ina35-year-oldwoman.Contrast-enhancedCTscanshowsanincidentallynotedanteriormediastinalcysticlesionwithirregularwallsandseparatedareas.Thelesionwassurgicallyremoved,andpathologicanalysisdemonstratedathymiccyst.3.胸腺囊腫CASE4

Cysticchangeofthethymusina28-year-oldmanwithHodgkinlymphomatreated3yearsearlier.Contrast-enhancedCTscanshowsathymiccyst(arrow)andthymicreboundhyperplasia(arrowhead).1.胸腺上皮細(xì)胞腫瘤：胸腺瘤（二）腫瘤病變低危組高危組胸腺癌TheWHOclassificationschemecorrelateswithinvasiveness:TypesAandABareusuallyclinicallybenignandencapsulated(stageI),typeBhasagreaterlikelihoodofinvasiveness(especiallytypeB3),andtypeCisalmostalwaysinvasive.胸腺瘤占成人前縱隔腫瘤20%，是成人前縱隔常見(jiàn)的原發(fā)腫瘤，好發(fā)于>40歲者，無(wú)性別差異。15%MG病人伴有胸腺瘤，而30%-50%胸腺瘤病人發(fā)生MG。胸腺瘤的病理特征為其在組織學(xué)上起源于胸腺的上皮性和淋巴細(xì)胞性成分，因而常按其上皮細(xì)胞和淋巴細(xì)胞的比例而分類。以上皮細(xì)胞為主的胸腺瘤預(yù)后最差。非侵襲性胸腺瘤:圓形、卵圓形或分葉狀腫塊;邊界清晰;多數(shù)密度均勻,也可發(fā)生囊變;腫瘤內(nèi)可見(jiàn)鈣化;大部分腫瘤生長(zhǎng)不對(duì)稱,居于前縱隔的一側(cè)；直徑<2cm的胸腺瘤可僅表現(xiàn)為正常胸腺邊緣局部隆起。不規(guī)則輪廓邊緣毛糙／不清縱隔脂肪層渾濁／消失淋巴結(jié)腫大胸膜侵犯、血管侵犯、其它臟器侵犯遠(yuǎn)處轉(zhuǎn)移不均勻強(qiáng)化低危高危胸腺癌侵襲性胸腺瘤明確的CT征象：縱隔結(jié)構(gòu)的包繞，直接侵犯中心靜脈、心包或胸膜種植轉(zhuǎn)移和晚期發(fā)生的跨膈肌擴(kuò)散。

Thymomatendstospreadalongthepleuralsurfacesandmayextendintotheabdomenviatheretrocruralspace.(A)Smalldiscretepleuralimplant(blackarrow),visualizedtoadvantageonlungwindow.(B)Leftretrocruralspread(whitearrow).(C)Retroperitonealimplant(blackshortarrow).胸腺癌WHO被分為C型，具有胸腺以外的細(xì)胞結(jié)構(gòu)特征，缺乏成熟的淋巴細(xì)胞。診斷需排除其他部位的原發(fā)腫瘤，因其組織學(xué)特征類似于起源于胸腺外的癌。少伴有重癥肌無(wú)力。CT表現(xiàn)為前縱隔大的腫物，具有侵襲性特點(diǎn)，特點(diǎn)與侵襲性胸腺瘤非常相似。但淋巴性及血源性轉(zhuǎn)移幾乎僅見(jiàn)于胸腺癌。胸腺癌Thymicsquamouscellcarcinomaina40-year-oldmale.(A,B)Largeheterogenousmassextendingalongthepericardium,withprobableinvasion(arrows).(C)SixweeksfollowingaChamberlainprocedure(leftanteriorthoracotomy)thereisnewchestwallinvasion,compatiblewithtumorseedinginthesurgicalwound.2.胸腺非上皮性腫瘤（1）胸腺淋巴瘤原發(fā)于胸腺的淋巴瘤少見(jiàn)，臨床上一半以上都是淋巴瘤侵及胸腺，且大多數(shù)HD累及胸腺。以結(jié)節(jié)硬化型、女性多見(jiàn)。原發(fā)與繼發(fā)鑒別困難。CT常表現(xiàn)為胸腺體積增大，前中縱隔多發(fā)腫大淋巴結(jié)或融合成團(tuán)塊狀腫大淋巴結(jié)，邊界清晰，增強(qiáng)掃描為均勻或不均勻強(qiáng)化。與胸腺瘤需鑒別：a.胸腺瘤常伴有壞死和囊變，增強(qiáng)掃描除囊變壞死區(qū)域，其他區(qū)域強(qiáng)化較均勻。b.淋巴瘤放療前無(wú)鈣化，25%胸腺瘤有鈣化。c.全身淋巴結(jié)腫大支持淋巴瘤診斷。d.發(fā)病年齡。鑒別：胸腺瘤，胸腺增生與胸腺增生鑒別：a.胸腺增生通常為對(duì)稱性體積增大；b.胸腺淋巴瘤多處淋巴結(jié)腫大。ConcurrentthymicandlymphnodeinvolvementbyHodgkinlymphomaina51-year-oldwoman.(A)Contrast-enhancedCTscanshowsinvolvementoftheleftlobeofthethymus(arrow)andsubcarinallymphnodes(arrowhead).(B)CoronalPETimageshowsasymmetricFDGavidityoftheleftthymiclobe(arrow)andsubcarinallymphnodes(arrowhead).

ABCase1ThymicinvolvementbyHodgkinlymphomainan18-year-oldman.AxialPET/CT(A)andcoronalPET(B)imagesshowcervicalandaxillaryadenopathy(arrowheadsinB)andasymmetricFDGuptakebythethymus(arrow).ABCase2（2）胸腺類癌胸腺類癌是一種較罕見(jiàn)、分化良好的神經(jīng)內(nèi)分泌腫瘤。平均發(fā)病年齡為40歲，男性發(fā)病率為女性三倍?；颊咄ǔ１憩F(xiàn)為內(nèi)分泌紊亂，如Cushing綜合癥(25%–40%)，MENI,MENII綜合癥（20%)。切除后易復(fù)發(fā)。病理上，胸腺類癌表現(xiàn)為巨大腫塊，直徑范圍6-20cm，平均11cm。大約50％的病灶有包膜，多數(shù)包膜完整。胸腺類癌常侵及鄰近的縱隔和其他胸內(nèi)結(jié)構(gòu)，它們常轉(zhuǎn)移到局部淋巴結(jié)、皮膚、腎上腺和骨骼，也見(jiàn)有報(bào)道轉(zhuǎn)移到肺、胸膜、顱腦和腎臟。大約50%的病人在發(fā)現(xiàn)時(shí)已經(jīng)有侵襲或者轉(zhuǎn)移病灶。CT表現(xiàn)缺乏特異性，不易與侵襲性胸腺瘤鑒別。需結(jié)合臨床。Thymiccarcinoidtumorina22-year-oldmanwitha3-monthhistoryofapersistentdrycough.(A)Contrast-enhancedCTscanshowsaheterogeneouslyenhancingthymicmass(arrow).(B)PETimageshowsintenseFDGuptakebythemass(arrow).NotethenodularcontourofthemassinbothAandB;contrastthatappearancewiththehomogeneoustextureandsmoothcontourincasesofthymicreboundhyperplasia.

Case1ABCase2Thymiccarcinoidina74-year-oldman.Contrast-enhancedCTscandemonstratesalobulated,heterogeneouslyenhancingmassintheanteriormediastinum.Notethelossofthefatplanebetweenthemassandthepericardium,afindingthatsuggestsinvasiveness.Photomicrograph(originalmagnification,40;H-Estain)showstumorcellsinatrabeculargrowthpatternwithoncocyticcytoplasmandovaltoirregularnuclearcontours.Case3Thymiccarcinoidina62-year-oldman.Non-contrastandContrast-enhancedCTscandemonstratesalobulated(FigA),heterogeneouslyenhancing(FigB)massintheanteriormediastinum.Notethelossofthefatplanebetweenthemassandthepericardium,afindingthatsuggestsinvasiveness.AB（3）胸腺脂肪瘤胸腺脂肪瘤是前縱隔少見(jiàn)腫瘤，混合了脂肪、胸腺上皮和淋巴組織，占胸腺腫瘤的5％，可發(fā)生在任何年齡段，無(wú)性別傾向。胸腺脂肪瘤一般預(yù)后良好，手術(shù)切除后不復(fù)發(fā)。體積通常較大，典型胸腺脂肪瘤CT掃描表現(xiàn)為前縱隔巨大腫塊，其內(nèi)可見(jiàn)脂肪、纖維分隔、正常胸腺組織。不典型畸胎瘤，膈疝Thymolipomaina14-year-oldgirlwitha2-weekhistoryofcoughandfever.(A)Contrast-enhancedCTscanshowsalarge,mostlyfattymass(arrows)inthelefthemithorax.Themasscausesminimal(ifany)displacementoftheheart.(B)CoronalT1-weightedMRimageshowsthemass(arrows),whichhasfibrousseptaandreplacesandassumestheshapeofthecollapsedlung.Afterresectionofthemass,theleftlungfullyexpanded。ABCase1Thymolipomaandthymolipomamimic.(A)Thymolipomamanifestingasalargefattymasscontainingsmallamountsofsofttissue,fillingtheentirerighthemithorax.

(B,C)Morgagniherniacontainingomentalfat,simulatingh