胰腺內(nèi)副脾表皮樣囊腫的影像特征及病理對照

楊雪融　周良平△　黃　丹

(1復旦大學附屬腫瘤醫(yī)院放射科-復旦大學上海醫(yī)學院腫瘤學系,2病理科　上海　200032)

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胰腺內(nèi)副脾表皮樣囊腫的影像特征及病理對照

楊雪融1周良平1△黃丹2

(1復旦大學附屬腫瘤醫(yī)院放射科-復旦大學上海醫(yī)學院腫瘤學系,2病理科上海200032)

目的探討胰腺內(nèi)副脾表皮樣囊腫(epidermoid cyst in intrapancreatic accessory spleen,ECIPAS)的影像學特征,以提高對該少見病變的認識。方法回顧性分析經(jīng)手術(shù)病理證實的5例ECIPAS的臨床、影像及病理資料。4例行CT平掃加雙期增強檢查,其中2例同時行磁共振胰膽管造影(magnetic resonance cholangiopancreatography,MRCP)檢查,1例行超聲內(nèi)鏡檢查,另1例行MR平掃加增強檢查。觀察病灶的大小、形態(tài)、密度信號及強化特點,并與組織病理進行對照。結(jié)果所有病灶均位于胰尾部,囊腫最大徑1.7～5.0 cm,平均2.7 cm。2例囊內(nèi)可見分隔。CT平掃3例為邊界清楚的類圓形低度灶,1例呈高密度伴邊緣點狀鈣化;增強后3例可見環(huán)繞囊腫的實質(zhì)顯著強化,動脈期和靜脈期密度均高于胰腺組織。1例MR掃描未見明顯實性成分,囊腫呈T1WI低信號,T2WI高信號。MRCP均未見囊腫與胰管相通。結(jié)論ECIPAS是少見的胰尾良性病變,其典型影像表現(xiàn)為囊腫伴周邊類脾臟強化的實性成分。

胰腺;副脾;表皮樣囊腫;體層攝影術(shù);X線計算機;磁共振成像;病理學

胰腺內(nèi)副脾表皮樣囊腫(epidermoid cyst in intrapancreatic accessory spleen,ECIPAS)由Davidson等[1]在1980年首次報道,是一種起源尚未明確的胰腺良性病變,臨床甚為少見,缺乏特征性臨床癥狀,誤診率極高[2]。因生物學行為和治療手段不同,ECIPAS與胰腺囊性腫瘤,如囊腺瘤等的鑒別診斷尤為重要,可靠的術(shù)前診斷能避免不必要的手術(shù)。目前國內(nèi)外有關(guān)ECIPAS的文獻多為個案報道,關(guān)注臨床病理方面較多而系統(tǒng)全面的影像學研究有限。本研究回顧性分析本院收治的5例ECIPAS患者的臨床資料、影像表現(xiàn)和病理結(jié)果,重點將術(shù)前影像與術(shù)后病理進行對照,并結(jié)合文獻探討,旨在提高對該少見病的認識及影像診斷準確率。

資 料 和 方 法

一般資料 收集2009年3月至2015年8月復旦大學附屬腫瘤醫(yī)院收治并經(jīng)手術(shù)病理證實的ECIPAS患者5例。其中女性4例,男性1例。年齡27～66歲,平均48歲。除1例因腹脹就診外,其余為體檢時腹部影像發(fā)現(xiàn)胰腺占位或腫瘤指標CA19-9升高。所有病例均無急性胰腺炎及腹部外傷史。

影像檢查CT檢查示:4例行CT平掃及雙期增強掃描。患者檢查前4 h禁食,掃描前口服溫水約800 mL適度充盈胃腔。采用Siemens Somatom Sensation MSCT掃描儀。管電壓120 kV,管電流300 mA,層厚5 mm。掃描范圍包括膈頂至髂棘水平。經(jīng)肘靜脈團注碘普羅胺(300 mg I/mL),劑量2 mL/kg,速率3.0 mL/s。注射對比劑后分別于25～30 s、60～65 s行動脈期和門脈期掃描。原始數(shù)據(jù)進行1.5 mm薄層重建及多平面重建。

MRI檢查示:1例行MR平掃加增強,2例行磁共振胰膽管造影(magnetic resonance cholangi-opancreatography，MRCP)。采用GE Signa 3.0 T磁共振掃描儀,8通道體部相控陣線圈。平掃序列為橫軸面FSPGR T1WI和FSE T2WI,層厚5 mm,間隔1 mm。增強掃描團注對比劑Gd-DTPA,劑量0.1 mmoL/kg,流率2 mL/s,序列LAVA(TR 2.5 ms,TE 1.2 ms),FOV 40 cm×40 cm。MRCP序列包括SSFSE T2WI(TR 1 090 ms,TE 78 ms),屏氣BH 2D MRCP(TR 7 000 ms,TE 1 235 ms),呼吸門控RTr 3D MRCP ASSET(TR 3 000 ms,TE 641 ms),FOV 32 cm×32 cm。

圖像分析 2名從事影像診斷工作10年以上的醫(yī)師共同閱片,結(jié)論不一致時協(xié)商統(tǒng)一。主要觀察病變部位、大小、邊界,有無鈣化,囊內(nèi)有無分隔和壁結(jié)節(jié),有無實性成分,CT、MR的平掃密度信號以及強化特征。另外還包括胰管是否擴張、病變是否侵犯周圍組織及有無淋巴結(jié)腫大等。

結(jié)　　　果

臨床特征 2例患者腫瘤指標CA19-9升高,分別為133.20和87.72 U/mL;CEA值均在正常范圍內(nèi)。術(shù)前影像學診斷2例為囊腺瘤,1例為實性假乳頭狀瘤,2例為胰腺良性囊腫,其中1例伴出血。因臨床上不除外腫瘤性病變,所有病例均行手術(shù)治療。1例行保留脾臟的胰尾切除術(shù),其余行胰尾聯(lián)合脾臟切除。除1例于2015年8月手術(shù)外,4例術(shù)后隨訪(平均11個月)實驗室檢查及影像未見復發(fā)(表1)。

影像表現(xiàn) 病灶均位于胰尾部,邊緣清楚,呈圓形或橢圓形,囊腫最大徑1.7～5.0 cm,平均2.7 cm。1例在超聲內(nèi)鏡上無回聲區(qū)內(nèi)探及分隔且部分融合,1例在MR T2WI上囊內(nèi)見細線樣低信號分隔。CT平掃1例為高密度,CT值約80 HU,邊緣見點狀鈣化(圖2);3例為低密度,CT值28～35 HU。1例囊內(nèi)壁不平呈結(jié)節(jié)樣改變(圖3),余例囊壁光滑。CT增強后3例可見環(huán)繞囊腫的實質(zhì)明顯強化,動脈期和靜脈期密度均高于周圍胰腺組織,強化方式與脾臟類似(圖1),實性成分對應在MRCP上呈T2WI高信號,同脾臟信號一致。MR檢查1例,未見實性成分,囊腫無強化,呈T1WI低信號,T2WI高信號(圖4)。MRCP均未見囊腫與胰管相通。所有患者均未見胰管擴張及淋巴結(jié)腫大與侵犯周圍征象。

表1　ECIPAS的臨床特征

Normal serum level of CA19-9 is 0-27 U/mL.SPT:Solid pseudopapillary tumor;DP: Distal pancreatectomy;S:Splenectomy.

A:Plain CT scan shows a well-defined lesion in the tail of the pancreas;B:Arterial phase scan shows the solid component surrounding the cyst with the same heterogeneous hyperdensity as the spleen;C:On portal phase the solid component shows the same density as the spleen which is higher than the pancreas;D:A microscopic slide reveals a cyst (circle) surrounded by accessory splenic tissue (star) in the pancreas parenchyma (triangle)(HE staining,×20).

圖11例66歲2.9 cm女性ECIPAS

Fig 1A 66-years-old women with 2.9 cm ECIPAS

A:Precontrast CT scan shows a high density lesion with stippled calcification;The lesion appears an unenhanced,low-density mass on arterial phase (B)and portal phase (C);D:Microscopic analysis reveal smuch amorphous secretion in the cyst (HE staining,×100).

圖21例53歲1.7 cm女性ECIPAS

Fig 2A 53-years-old women with 1.7 cm ECIPAS

病理檢查 手術(shù)標本表面光滑,切面顯示單房或多房囊腫,囊液淡黃至渾濁,周圍覆以褐色質(zhì)軟組織。HE染色切片鏡下囊壁內(nèi)襯復層鱗狀上皮,部分角化,無皮脂腺等皮膚附屬器,周圍為副脾組織,可見紅髓、白髓及脾小梁。脾與胰腺之間有纖維間隔。1例囊內(nèi)見大片無定形分泌物,同時伴膽固醇結(jié)晶及鈣化。1例囊內(nèi)壁不光整,可見由纖維成分及少量脾組織構(gòu)成數(shù)枚凸起。

Portal phase CT (A) and MR T2WI (B) images show the inner surface of cystic wall unsmooth with a mural nodule;C:The histological section shows thick fibrous tissue with hyaline degeneration and spleen tissue resembling a mural nodule (HE staining,×40).

圖31例27歲5.0 cm女性ECIPAS

Fig 3A 27-years-old women with 1.7 cm ECIPAS

The cyst shows low signal intensity on T1WI (A),high signal intensity on T2WI (B),and remains unenhanced after contrast administration (C).No heterotopic splenic tissue is visible.D:Histopathological examination (HE staining,×400) shows that the cyst is lined with stratified squamous epithelium.Subepithelial structure consistents with features of the spleen.

圖41例52歲2.0 cm女性ECIPAS

Fig 4A 52-year-old women with 2.0 cm ECIPAS

討　　　論

概述 ECIPAS是一種少見的胰腺良性病變,據(jù)不完全統(tǒng)計,目前中英文文獻報道僅數(shù)十例[2,3]。患者年齡12～70歲,平均45歲,女性多于男性(1.45∶1),多無臨床癥狀,部分出現(xiàn)腹痛、腹脹、惡心、嘔吐等非特異性表現(xiàn)[3]。值得一提的是發(fā)病人群中亞洲人占大多數(shù)(28/36,77.7%)[2],有明顯種族傾向。本研究中女性4例、男性1例,平均年齡48歲,除1例腹脹外,其余臨床表現(xiàn)無殊,與文獻基本相符。

本組2例CA19-9升高,同時伴消化道腫瘤指標CA50和CA242輕度升高,或為病灶周圍胰腺組織的反應性結(jié)果。但Higaki等[4]指出ECIPAS患者血清CA19-9和CEA升高是由囊壁內(nèi)襯鱗狀上皮產(chǎn)生后釋放入循環(huán)。多個相關(guān)研究[5-6]中免疫組化證實內(nèi)襯上皮細胞CA19-9和CEA表達陽性,并且術(shù)后腫瘤指標降低也支持這一理論。本組血清CEA均未升高,有待進一步大樣本臨床病理研究。

副脾是正常脾組織的先天異位,臨床上并不少見,多位于脾門,尸檢研究中9.3%的副脾在胰尾部[7]。ECIPAS的組織起源尚有爭議,根據(jù)原位脾臟表皮樣囊腫的發(fā)生方式，有的認為由間皮鱗狀上皮化生[8]形成,另外還有胚胎鱗狀上皮內(nèi)陷[9]、胰管突入副脾[10]等假說。盡管是良性病變,但某些病例中ECIPAS可迅速增大。本研究中1例體檢發(fā)現(xiàn)胰尾1.5 cm大小的囊性占位,1年后復查病灶為2.9 cm。Kumamoto等[11]報道1例隨訪1年的ECIPAS,從2.0 cm增大至3.8 cm。對此類患者建議采用創(chuàng)傷較小、保留脾臟的腹腔鏡下胰尾切除術(shù)。

影像表現(xiàn) 文獻報道ECIPAS均位于胰尾部,大小1.4～15 cm,平均3.9 cm[2]。囊內(nèi)可有分隔,單房囊腫約為多房囊腫的1.5倍[12]。本組1例在超聲內(nèi)鏡、1例在MR上囊內(nèi)見薄壁分隔,MR具有高軟組織分辨率,相比CT能更好地顯示內(nèi)部細微結(jié)構(gòu)。CT平掃一般為低密度灶,本組1例呈高密度,CT值約80 HU,影像診斷囊腫伴出血,病理顯示囊內(nèi)大片無定形分泌物為蛋白樣物質(zhì)。囊腫呈T1WI低信號,T2WI高信號,部分研究中ECIPAS T1WI為高信號[5,13],考慮與囊液角蛋白含量高有關(guān)[14]。

囊腫并無突出特征,確認副脾組織存在是診斷ECIPAS的關(guān)鍵,少量副脾影像上不易明確,因此正確的術(shù)前診斷很大程度依賴于囊腫周圍有足夠多的脾組織。Motosugi等[12]回顧性分析33例ECIPAS,其中15例在影像或大體病理上副脾不可見,又將18例可見副脾的形態(tài)分為腫塊樣(三角形或帆狀)和環(huán)狀(厚薄均一),兩者比例為13∶5。本組1例MR上副脾不明顯,但鏡下病理清晰可見脾組織和內(nèi)襯鱗狀上皮結(jié)構(gòu);3例CT上可見副脾,按Motosugi等[12]的分類都為腫塊樣環(huán)繞囊腫,動脈期明顯不均勻強化,靜脈期強化程度趨于均勻,二期密度均高于周圍胰腺。同時,T2WI上副脾同原位脾一致,呈高信號,與低信號的胰腺區(qū)分(本研究MRCP檢查未含T1WI序列)。除強化特征外,超順磁氧化鐵對比劑MR成像上,因脾臟網(wǎng)狀內(nèi)皮組織吞噬作用,副脾同原位脾均出現(xiàn)T2WI信號降低[15],也可證實為胰腺內(nèi)副脾。本組1例見點狀鈣化,其他報道也多為病灶邊緣小鈣化[13,16]。

鑒別診斷 胰腺囊性病灶一般分為腫瘤性和非腫瘤性,生物學行為和治療方式差別很大。非腫瘤性囊性病變最常見的是假性囊腫[17],多有胰腺炎或外傷史,出血,胰液外滲,組織壞死包裹,囊壁為纖維肉芽組織,壁薄伴強化,囊壁可鈣化。潴留囊腫是梗阻所致的胰腺導管囊狀擴張,識別下游的結(jié)石、腫瘤或其他引起導管狹窄的病因后也不難診斷。另外如單純囊腫、淋巴上皮囊腫等很少見,影像學表現(xiàn)一般考慮為良性。

與ECIPAS鑒別的腫瘤性病變主要為囊腺瘤、實性假乳頭狀腫瘤(solid pseudopapillary tumor,SPT)和導管內(nèi)乳頭狀黏液瘤(intraductal papillary mucinous neoplasm,IPMN),導管腺癌伴囊變通常惡性征象顯著,容易除外。本組2例診斷為囊腺瘤,為中老年女性。其中1例CT增強上可見胰尾部環(huán)繞囊腫的實質(zhì)成分強化方式與原位脾一致,為ECIPAS的典型表現(xiàn),但最初對其缺乏認識而未列入鑒別診斷。另1例未見明顯實性成分,T2WI上高信號的囊腫內(nèi)隱約可見低信號線樣分隔。囊腺瘤分漿液性和黏液性,前者為良性而后者具有惡性潛能。漿液性囊腺瘤(serouscystadenoma,SCA)微囊型為多囊的蜂窩狀腫塊,而寡囊型表現(xiàn)為單個或數(shù)個大囊,與副脾不明顯的ECIPAS可相似,但寡囊型SCA多位于胰頭,呈分葉狀,囊壁無強化[18]。黏液性囊性腫瘤(mucinous cystic neoplasm,MCN)多位于胰體尾部,呈多房大囊樣(>2cm),可見厚壁強化及壁結(jié)節(jié)[19]。將ECIPAS的副脾誤認為MCN的厚壁,加之兩者相似的發(fā)病年齡性別及部位,ECIPAS常被誤診為MCN[2]。本組1例囊內(nèi)壁不平伴結(jié)節(jié)樣改變,Yamanishi等[20]報道1例超聲內(nèi)鏡上可見壁結(jié)節(jié)的ECIPAS,同樣都經(jīng)病理證實結(jié)節(jié)由纖維組織伴玻璃樣變性及脾組織構(gòu)成。

本組1例考慮到年輕女性(27歲)胰尾囊實性占位,診斷為SPT。SPT是好發(fā)于年輕女性的交界性腫瘤,通常較大,胰頭和胰尾多見,囊性和實性成分可不同比例混合,實性成分多漸進性強化,但強化程度低于胰腺實質(zhì)[21]。IPMN起源于主胰管或分支胰管,老年男性居多,常發(fā)生在胰頭鉤突部,MRCP顯示胰管擴張與病灶相通等特點[22],易于區(qū)分。因ECIPAS的副脾明顯強化,有時與富血供的胰腺神經(jīng)內(nèi)分泌腫瘤(pancreatic neuroendocrine tumors,PNETs)囊變難以鑒別。無功能性PNETs不伴激素相關(guān)臨床癥狀,發(fā)現(xiàn)時多較大,可有囊變,Kawamoto等[23]報道13例囊性為主的PNETs有11例表現(xiàn)為周邊強化且高于胰腺實質(zhì)。超聲內(nèi)鏡及其引導下針吸活檢提供了高分辨率的形態(tài)學、對囊液生化分析及細胞學檢測,是CT、MR等影像檢查的有益補充[24]。

綜上所述,ECIPAS為少見的胰尾良性病變,明確診斷能避免不必要的手術(shù)或提供適當?shù)氖中g(shù)方式。ECIPAS缺乏特征性臨床癥狀和實驗室指標,發(fā)病具有女性優(yōu)勢。鑒別胰尾囊性病變時有典型表現(xiàn)如囊腫伴周邊類脾臟強化的實性成分應考慮此病。

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The imaging features of epidermoid cyst in intrapancreatic accessory spleen:correlated with pathological findings

YANG Xue-rong1, ZHOU Liang-ping1△, HUANG Dan2

(1DepartmentofRadiology-DepartmentofOncology,ShanghaiMedicalCollege,2DepartmentofPathology,ShanghaiCancerCenter,FudanUniversity,Shanghai200032,China)

ObjectiveTo investigate the imaging features of epidermoid cyst in intrapancreatic accessory spleen (ECIPAS) for better understanding of the rare disease.MethodsThe clinical,radiological and pathological data of 5 patients with pathologically confirmed ECIPAS were retrospectively reviewed.Four cases underwent plain and dual-phase enhancement CT scan,of which 2 cases received magnetic resonance cholangiopancreatography (MRCP),and 1 case received endoscopic ultrasonography,and the other 1 case underwent plain and contrast-enhanced MRI scan.The size,shape,density/signal and enhancement mode of the lesions were analyzed and correlated with pathologic findings.ResultsAll lesions were situated in the pancreatic tail,wherein the mean size of the cyst was 2.7 cm,ranging from 1.7 cm to 5.0 cm.The cyst appeared multilocular in 2 cases.On plain CT,3 cases showed oval well-defined low density foci,while 1 case showed high density with stippled calcification in the periphery.In 3 cases,the solid component surrounding the cyst displayed marked enhancement on postcontrast CT,which density were higher than the pancreatic parenchymaduring both arterial and portal venous phase.Solid component was not seen on MR in 1 case,the cyst was hypo-intense on T1WI and hyper-intense on T2WI.No communication with pancreatic duct was shown on MRCP.ConclusionsECIPAS is a rare benign lesion situated in the tail of the pancreas,the typical imaging manifestation is a cyst with surrounding solid component that enhancing similar to the spleen.

pancreas;accessory spleen;epidermoid cyst;body section radiography;X-ray computed tomography; magnetic resonance imaging;pathology

R816.5

Bdoi: 10.3969/j.issn.1672-8467.2016.04.010

2015-10-15;編輯:沈玲)