正常胸腺及胸腺病變的ct表現(xiàn)呂曉飛

1、正常胸腺及胸腺病變—CT表現(xiàn) The Normal and Abnormal Thymus —— CT imaging finding,南方醫(yī)院影像中心2009級博士研究生呂曉飛,Content,胸腺是一種復(fù)雜的淋巴上皮器官，具有調(diào)節(jié)細胞免疫的功能，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，有利于評價是否正常及胸腺病變的范圍。,正常CT表現(xiàn)（形態(tài)、大小、密度）,胚胎發(fā)育,正常胸腺解剖位置及異位胸

2、腺,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)的小淋巴樣細胞移行至胸腺始基；第14~16周，胸腺進一步分化形成皮質(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脈弓。 胸腺的位置上界

3、不超過胸骨柄上緣，下緣不超過左心室上緣或主動脈根部層面，外緣不超過上腔靜脈、主動彌弓外緣．其前緣位置正常可隨周圍結(jié)構(gòu)改變而向左或向右移位。,正常胸腺解剖,異位胸腺,Ectopic and accessory thymic tissue may occur anywhere along the path of descent (thymopharyngeal duct) as the result of failure of descen

4、t, sequestration, or failure to involute. Ectopic or accessory thymic tissue may be found in the vicinity of the superior vena cava, brachiocephalic vessels, and aorta. Rarely, it may be found in the posterior mediastinu

5、m or even in the dermis .,異位胸腺,Figure 1. Normal thymus with a cervical component in a 12-year-old boy. (a) Sagittal ultrasonographic (US) image shows the mediastinal and cervical components of the thymus (black arrows) a

6、ttached to the lower pole of the thyroid (white arrow) via the thyrothymic ligament (arrowhead). Note the “starry sky” appearance of the thymus; this is created by hyperechoic fat against the background of the remaining

7、hypoechoic lymphoid tissue. (b) Corresponding anatomic drawing shows the mediastinal (arrowheads) and cervical (arrows) components of the thymus.,異位胸腺,Figure 2. Cervical component of the thymus in a 3-year-old boy with a

8、 strong maternal family history of papillary thyroid carcinoma. The cervical component was misinterpreted as an “exophytic tumor of the thyroid gland.” Contrast-enhanced CT scans show a normal mediastinal thymus (arrows

9、in A) and its cervical component (arrows in B). Follow-up studies 2 years later showed no change, and the patient remained asymptomatic.,異位胸腺,Figure 3. Ectopic parapharyngeal thymus in a 7-week-old boy with a “mass” in t

10、he right mandib-ular angle. Coronal contrast material–enhanced T1-weighted magnetic resonance (MR) image shows an enhancing parapharyngeal mass (arrow), which is isointense relative to the mediastinal thymus (arrowhead).

11、 At needle biopsy, the mass was proved to be ectopic thymic tissue.,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)（大小）,胸腺的形態(tài)隨年齡而異，年輕人（特別是25歲以下者）的正常胸腺的大小和重量有較大的差異。,國內(nèi)研究學(xué)者認為胸腺的厚度隨年齡變化，變化最大是在20-49歲之間，總體來說是從大到小再到大，大于60歲有增大趨勢；6

12、0歲，可超過30mm。寬度則隨年齡增大而增大。,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歲后胸腺進一步萎縮，不再能見到明確的軟組織密度 的胸腺結(jié)構(gòu)，但可見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

13、人而異。在83%的小于50歲的 人群中還可見正常胸腺。此后前縱隔完全脂肪化，但大部分人還可見到密度稍高于 脂肪的殘存的纖維性胸腺框架。,NORMAL or ABNORMAL??,On the basis of this review, we have drawn the following conclusions regarding the appearance of the thymus gland a

14、nd the detection of thymic abnormalities:The thymus gland is largest at puberty, and its overall size does not change significantly with age. It occupies essentially all of the mediastinal compartment anterior to the a

15、ortic arch, superior vena cava, and great vessels throughout life.2. After puberty, parenchymal atrophy within the gland occurs, with the greatest percentage of parenchymal replacement by fat occurring between the ages

16、of 31 and 40.3. After age 40, the presence of a spherical or oval focal soft-tissue mass within the thymus gland usually represent a neoplasm.4. Before age 40, differentiation of a small thymoma from normal residual th

17、ymic parenchymal tissue may be impossible on the basis of size alone.5. At all ages, a thymoma usually produces a focal bulge in the normally smooth adjacent visceral-pleural surface.,Moore, A.V., et al. , Age-related c

18、hanges in the thymus gland: CT-pathologic correlation. AJR Am J Roentgenol, 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）縱隔生殖細胞瘤,1.胸腺增生,胸腺真性

19、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于機體遇到各種應(yīng)激事件，免疫處于較大的挑戰(zhàn)時期，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。 胸腺彌漫性增大，但仍維持正常形態(tài)，兩緣對稱，呈光滑的不分葉的外形，CT值與正常者相似。

20、,（一）非腫瘤病變,Case 2 胸腺真性增生，14歲，男。原發(fā)性T細胞淋巴瘤化療后。,Case 1 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。,2.胸腺淋巴樣（濾泡性）增生,好發(fā)于青壯年，多為15-35歲女性。常見于重癥肌無力（MG）患者，65%左右重癥肌無力病人顯示有淋巴濾泡性胸腺增生。它也被稱為自家免疫性“胸腺炎”，較真性胸腺增生多見，此時，胸

21、腺的大小和質(zhì)量正常，但髓質(zhì)擴張，而皮質(zhì)受損。 胸腺可正常或增大，常是在MG病人行胸腺切除中發(fā)現(xiàn)并診斷的。據(jù)報道，在患MG并經(jīng)病理證實有胸腺增生的病人中，25% -50 %的病例在CT上胸腺的大小正常；如有增大則可表現(xiàn)為彌漫性增大，使原略內(nèi)陷的外緣變?yōu)槁⊥?；有的則出現(xiàn)局灶性結(jié)節(jié)或大至5cm 的腫塊。CT診斷胸腺淋巴樣增生有一定的限度。,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

22、見，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，但最常見于前上縱隔胸腺區(qū)。頸部胸腺囊腫最常見于3-8歲兒童，縱隔胸腺囊腫多見于成人。多無癥狀，偶在查體或因囊腫大有壓迫癥狀，如胸悶不適、胸痛行X線檢查時被發(fā)現(xiàn)。（2）獲得性胸腺囊腫，常見原因為感染，但也有認為Hassall氏小體擴張構(gòu)成，好發(fā)于無癥狀的男性。有報道在免疫缺陷病毒

23、感染的無癥狀的患者中可發(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，甚至掩蓋了原來的腫瘤，但后者從未見有完全囊變而形成薄壁囊腫者。,3.胸腺囊腫,先天性胸腺囊腫表現(xiàn)為位于前縱隔內(nèi)一側(cè)性邊緣清楚的單房或多房的囊性腫塊。囊壁薄或不可見，囊內(nèi)可有分隔，壁可有鈣化。囊內(nèi)的CT值常為水樣密度，但也有高密度者。在兒童中伴有向頸部延伸的先天性胸腺囊腫與淋巴管

24、瘤不能區(qū)分。在CT上區(qū)別胸腺囊腫為先天性或后天性具有一定的意義，因后天性者在手術(shù)后可復(fù)發(fā)、可伴有胸腺瘤或胸腺癌等腫瘤或因與鄰近組織粘連而在術(shù)中被誤認為侵襲性腫瘤。后天性胸腺囊腫表現(xiàn)為邊緣欠清楚、密度不均勻、單房或多房的囊性腫塊，以多房者多見。如CT上見到有明確的囊壁或伴有鈣化時強烈提示為后天性者。,胸腺瘤，縱隔囊性畸胎瘤（皮樣囊腫），支氣管囊腫,3.胸腺囊腫,CASE 1 Thymic cyst in a 66-year-old

25、woman. (A) Contrast-enhanced CT scan shows an incidentally noted anterior mediastinal lesion (arrow) with well-circumscribed borders and soft-tissue attenuation. The lesion is indistinguishable from a solid mass. (B) On

26、a T2-weighted MR image, the lesion (arrow) is hyperintense and contains a fluid level, findings that indicate a hemorrhagic or mucin-containing cystic lesion. The lesion was surgically removed, and pathologic analysis de

27、monstrated a thymic cyst.,3.胸腺囊腫,CASE 2 Thymic cyst associated with infection in a 35-year-old woman. Contrast-enhanced CT scan shows an incidentally noted anterior mediastinal cystic lesion with irregular walls and sepa

28、rated areas. The lesion was surgically removed, and pathologic analysis demonstrated a thymic cyst.,3.胸腺囊腫,CASE 3 Cystic thymoma in a 48-year-old woman. Axial short inversion time inversion-recovery MR image shows hyperi

29、ntense cystic lesions in the mediastinum abutting the pericardium. Note the hypointense nodular lesion (arrow), a finding that suggests the presence of a solid component. The nodule demonstrated enhancement after contras

30、t material administration. Surgery was performed, and pathologic analysis helped confirm a cystic type AB thymoma.,3.胸腺囊腫,CASE 4 Cystic change of the thymus in a 28-year-old man with Hodgkin lymphoma treated 3 years earl

31、ier. Contrast-enhanced CT scan shows a thymic cyst (arrow) and thymic rebound hyperplasia (arrowhead).,1.胸腺上皮細胞腫瘤：胸腺瘤,（二）腫瘤病變,,,,低危組,高危組,胸腺癌,The WHO classification scheme correlates with invasiveness: Types A and AB are

32、usually clinically benign and encapsulated (stage I), type B has a greater likelihood of invasiveness (especially type B3), and type C is almost always invasive.,胸腺瘤占成人前縱隔腫瘤20%，是成人前縱隔常見的原發(fā)腫瘤，好發(fā)于>40歲者，無性別差異。15%MG病人伴有胸腺

33、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胞性成分，因而常按其上皮細胞和淋巴細胞的比例而分類。以上皮細胞為主的胸腺瘤預(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)可見鈣化;大部分腫瘤生長不對稱,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。,Case 1 57歲，女性Case 2

34、49歲，男性Case 2 58歲，女性Case 2 45歲，男性,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、其它臟器侵犯遠處轉(zhuǎn)移不均勻強化,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)生的跨膈肌擴散。,Thymoma tends to spread along the pleural surfa

35、ces and may extend into the abdomen via theretrocrural space. (A) Small discrete pleural implant (black arrow), visualized to advantage on lung window.(B) Left retrocrural spread (white arrow). (C) Retroperitoneal impla

36、nt (black short arrow).,胸腺癌,WHO被分為C型，具有胸腺以外的細胞結(jié)構(gòu)特征，缺乏成熟的淋巴細胞。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。少伴有重癥肌無力。CT表現(xiàn)為前縱隔大的腫物，具有侵襲性特點，特點與侵襲性胸腺瘤非常相似。但淋巴性及血源性轉(zhuǎn)移幾乎僅見于胸腺癌。,胸腺癌,Thymic squamous cell carcinoma in a 40-year-old male.

37、 (A, B) Large heterogenous mass extending along the pericardium, with probable invasion (arrows). (C) Six weeks following a Chamberlain procedure (left anterior thoracotomy) there is new chest wall invasion, compatible w

38、ith tumor seeding in the surgical wound.,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，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。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)或融合成團塊狀腫大淋巴結(jié)，邊界清晰，增強掃描為均勻或不均勻強化。,與胸腺瘤需鑒別：a.胸腺瘤常伴有壞死和囊變，增強掃描除囊變壞死區(qū)域，其他區(qū)

39、域強化較均勻。b.淋巴瘤放療前無鈣化，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.胸腺增生通常為對稱性體積增大；b.胸腺淋巴瘤多處淋巴結(jié)腫大。,Concurrent thymic and lymph node involvement by Hodgkin lymphoma in a 51-year-old woman. (A) Contrast-enhanc

40、ed CT scan shows involvement of the left lobe of the thymus (arrow) and subcarinal lymph nodes (arrowhead). (B) Coronal PET image shows asymmetric FDG avidity of the left thymic lobe (arrow) and subcarinal lymph nodes (a

41、rrowhead).,A,B,Case 1,Thymic involvement by Hodgkin lymphoma in an 18-year-old man. Axial PET/CT (A) and coronal PET (B) images show cervical and axillary adenopathy (arrowheads in B) and asymmetric FDG uptake by the thy

42、mus (arrow).,A,B,Case 2,（2）胸腺類癌,胸腺類癌是一種較罕見、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)

43、移到局部淋巴結(jié)、皮膚、腎上腺和骨骼，也見有報道轉(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。,Thymic carcinoid tumor in a 22-year-old man with a 3-month history of a persistent dry cough. (A) Contrast-enhanced CT scan shows

44、 a heterogeneously enhancing thymic mass (arrow). (B) PET image shows intense FDG uptake by the mass (arrow). Note the nodular contour of the mass in both A and B; contrast that appearance with the homogeneous texture an

45、d smooth contour in cases of thymic rebound hyperplasia.,Case 1,A,B,Case 2,Thymic carcinoid in a 74-year-old man. Contrast-enhanced CT scan demonstrates a lobulated, heterogeneously enhancing mass in the anterior mediast

46、inum. Note the loss of the fat plane between the mass and the pericardium, a finding that suggests invasiveness. Photomicrograph (original magnification, 40; H-E stain) shows tumor cells in a trabecular growth pattern wi

47、th oncocytic cytoplasm and oval to irregular nuclear contours.,Case 3,Thymic carcinoid in a 62-year-old man. Non-contrast and Contrast-enhanced CT scan demonstrates a lobulated (Fig A), heterogeneously enhancing (Fig B)

48、mass in the anterior mediastinum. Note the loss of the fat plane between the mass and the pericardium, a finding that suggests invasiveness.,A,B,（3）胸腺脂肪瘤,胸腺脂肪瘤是前縱隔少見腫瘤，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，無性別傾向。胸腺脂肪瘤一般預(yù)后良好

49、，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)可見脂肪、纖維分隔、正常胸腺組織。,不典型畸胎瘤，膈疝,Thymolipoma in a 14-year-old girl with a 2-week history of cough and fever. (A) Contrast-enhanced CT scan shows a large, mostly fatty mass (arrows) i

50、n the left hemithorax. The mass causes minimal (if any) displacement of the heart. (B) Coronal T1-weighted MR image shows the mass (arrows), which has fibrous septa and replaces and assumes the shape of the collapsed lun

51、g. After resection of the mass, the left lung fully expanded。,A,B,Case 1,Thymolipoma and thymolipoma mimic. (A) Thymolipoma manifesting as a large fatty mass containing small amounts of soft tissue, filling the entire ri

52、ght hemithorax.,(B, C) Morgagni hernia containing omental fat, simulating hymolipoma. Mesenteric vessels (arrowheads) can be tracked into the hernia,suggesting the correct diagnosis.,Case 2,（4）縱隔胸腺生殖細胞腫瘤,生殖細胞腫瘤包括精原細胞瘤、非

53、精原細胞瘤（畸胎瘤、胚胎性癌、內(nèi)胚竇癌、絨毛膜癌）以及混合型?？v隔生殖細胞腫瘤是最常見的性腺外的生殖細胞腫瘤。多見于兒童和青少年。80%左右為良性，其中良性畸胎瘤占大部分?？v隔生殖細胞腫瘤發(fā)病率男性多于女性,其中惡性生殖細胞腫瘤男性發(fā)病率遠遠高于女性。血尿絨毛膜促性腺激素(HCG)、血甲胎球蛋白(AFP)及癌胚抗原（CEA）水平對本病臨床診斷有較高的參考價值?；チ稣伎v隔生殖細胞瘤的60%～70%，由3種胚胎性生殖細胞層中的至少

54、2種組成。通常表現(xiàn)為圓形或分葉狀腫塊，體積較大，突向中線一側(cè)。前縱隔囊性腫物內(nèi)有液體、軟組織、鈣化、脂肪等多種密度,是良性、成熟畸胎瘤的特征性表現(xiàn)。惡性者則邊界欠清晰，結(jié)節(jié)狀或團塊狀軟組織密度影為主。,A 43-year-old male with primary malignant mediastinal germ cell tumor demonstrating both fatty content and dense calcif

55、ication.,Case 1,Mature, benign teratoma in a 35-year-old male presenting with chest pain. (A) Anteriormediastinal heterogeneous mass, containing cystic and enhancing solid areas. (B) The mass appears to encase adjacent

56、mediastinal structures with no apparent separating fat plane. However, at surgery there was no invasion of these structures and complete resection was achieved.,Case 2,Thank You !,SOUTHERN MEDICAL UNIVERSITY,Lv Xiao-fei,