1、胃肠间质瘤(GIST)2009-01-01杨梅流行病学特点v胃肠道间质瘤（gastrointestinal stromal tumor，GIST）是一 种少见的源于胃肠道间质细胞的肿瘤，发病率约2/10 万，主 要发病人群在4070 岁，中位年龄58 岁，男性稍多于女性。v本病临床表现及影像 学所见缺乏特异性，确诊需要靠病理组织学及免疫组化检测。组织学特点vthe GIST cells are closely related to the interstitial cells of Cajal(ICC)v组织学上可表现为梭形细胞型、上皮细胞型，或两者的混 合型。v分子学上绝大多数该肿瘤表现为c
2、-kit基因的变异及少部分（约5%）患者PDGFRA基因的变异 v免疫组化绝大多数可检测到CD117 抗体阳性，表明组织 或细胞表达c-kit 原癌基因蛋白，即属赖氨酸激酶家族的 c-kit 原癌基因发生功能获得性突变导致。有50-year-old woman with small-bowel gastrointestinal stromal tumor(GIST).Photomicrograph of histopathologic slide shows typical GIST composed of fascicles of nondescript spindle cells.Appe
3、arance on H and E stain is similar to that of smoothmuscle tumor.免疫组化检查vThe tumours can be positive for KIT(95%),CD34(6070%),ACAT2(smooth muscle actin;3040%),S100(5%),DES(desmin;12%),and keratin(1-2%).KIT is the most specifi c and sensitive marker.。v另外，CD34（+），S-100（-），GFAP（-）有助于协助鉴别诊断，S-100（-）可除外神
4、经源性肿瘤，GFAP（-）可除外胶质瘤。临床特点v最常见的间质性肿瘤，仅占胃肠道肿瘤的1-3%。好发于胃（60-70%）、小肠（1/3）、结肠/直肠（5%）、食管（2%）。还有发生于网膜、肠系膜及后腹膜。v大多数间质瘤（约60-70%）为良性，且多发生于胃部。这些病灶多偶然发现，均可以手术切除。14的在眼底及贲门，75在胃体，11的胃窦。v目前趋向认为小肠间质瘤有潜在恶性倾向，推测其恶性程度的主要指标是肿瘤的大小及细胞核分裂相数目（每50HPF 下的数目）vFletcher 等2认为：肿瘤直径2 cm 和细胞核分裂相数目5/50HPF 为极低度恶性；直径25 cm 和5/50HPF 为低度恶性
5、；直径510 cm 和5/50HPF 或直径5 cm 和610/50HPF 为中度恶性；直径5 cm 和5/50HPF 或直径 10 cm 和10/50HPF 为高度恶性，但也有直径小的肿瘤发生 转移的报道。v。Chiappa 等3报道胃肠间质瘤术后复发或转移的时间是436 个月。v个别报道时间长达十几年。临床症状v临床症状主要取决于肿瘤的位置及大小，且无特异性的表现，仅表现为饱胀感、消化不良、腹痛及可触及包块等症状，偶尔症状由肿瘤内出血引起。v肿瘤出血是由于溃疡所致。v肿瘤常表现为起源于粘膜下向腔外生长的特性，很少引起肠梗阻。v十二指肠的间质瘤引起梗阻性黄疸时易与胰腺癌相混淆。肿瘤位于Vat
6、er壶腹部。钡餐检查v表现为粘膜下边缘清晰的充盈缺损。（Forty-two-year-old female with GIST at the gastroesophageal junction.）CT影像学征象v边界清晰不均质的肿块v边缘强化明显，厚度不均，中心密度减低。v原因是由于出血、坏死、囊变。Seventy-year-old male with GIST of the stomach with liver metastases.A large intraluminal mass is seen in the stomach,with heterogenous liver metasta
7、ses.v很多肿瘤发现时已经体积很大，约5-30cm，增强CT表现为不均质强化、腔外生长的肿块(Fig.2)。v较小的原发于胃的间质瘤表现为明显的强化(Fig.3)，在小肠的原发间质瘤很少有此征象。v小肠的间质瘤发现时已经很大且倾向于恶性，绝大多数病灶发生于十二指肠。v有的较大的肿瘤平扫时可发现出血Fig.2.48-year-old woman with small-bowel gastrointestinal stromal tumor.Axial contrast-enhanced CT scan of pelvis shows exophytic heterogeneously enha
8、ncing mass(arrow).Fig.3.30-year-old man with gastric gastrointestinal stromal tumor.Axial contrast enhanced CT scan of upper abdomen shows intense homogenous enhancement of tumor arising from gastric wall(arrow).v偶尔也会在CT上发现腔内的肿瘤(Fig.4).。v口服造影剂时可发现粘膜下溃疡(Fig.5)。v还有部分腔外的间质瘤被误诊为胰腺的肿瘤或假性囊肿(Fig.6)。肿瘤与肠管壁常
9、仅通过一个很薄的蒂相连，要认真辨认肿瘤的起源。v如果存在肠系膜转移，转移灶为边界清晰、边缘光滑，无牵拉改变(Fig.7)。Fig.4.69-year-old woman with gastric gastrointestinal stromal tumor.Axial contrast-enhanced CT scan of upper abdomen shows large intraluminal component of tumor(arrow).Fifty-six-year-old male with GIST of gastric fundus.Postcontrast CT sho
10、ws homogenous intraluminal GIST along the lesser curve,extending into the gastrohepatic ligament.Fig.5.Gastric gastrointestinal stromal tumor(GIST).A,Axial contrast-enhanced CT scan of upper abdomen of 69-year-old woman shows large intraluminal component of tumor with pocket of gas(arrow).B,In 63-ye
11、ar-old woman with gastric GIST,axial contrast-enhanced CT scan of upper abdomen shows large heterogeneously enhancing tumor in stomach and ulcer filled with oral contrast agent(arrow).Fig.6.30-year-old man with gastric gastrointestinal stromal tumor.B).This tumor was originally mistaken for infected
12、 pancreatic pseudocyst.fig.776-year-old man with small-bowel gastrointestinal stromal tumor.Axial contrast-enhanced CT scan of pelvis shows smooth mesenteric metastasis (arrowheads)at presentation.v和小肠的淋巴结相同，胃肠间质瘤可以是小肠管腔瘤样扩张。(Fig.8).v原因：肿瘤迅速生长。肿瘤破坏肌间神经丛。v原发肿瘤没有钙化，但是，在特殊化疗后的转移灶内偶尔会出现钙化。Fig.8.45-year-
13、old man with small-bowel gastrointestinal stromal tumor.A and B,Axial contrast-enhanced CT scans of mid abdomen show large mass(arrow)arising from small bowel,causing aneurysmal dilatation of bowel.Proximal(arrowheads)and distal segments of small bowel were of normal caliber.肿瘤如果与管腔交通，使肿瘤空洞化及窦道形成。Se
14、venty-seven-year-old male with GIST of the ileum.Postcontrast CTshows a large intra-abdominal mass with central cavitation.v肿瘤长大过程中，边缘光滑，仅推挤并不侵犯周围组织及血管。这一点可以与类癌及腺癌鉴别Fifty-six-year-old male with GIST of the ileum.(a)Postcontrast CTshows 12 cm,partially necrotic primary tumour arising from the small b
15、owel.直肠结肠的间质瘤表现为边界清晰的壁结节，向管腔内侵犯。Seventy-seven-year-old male with rectal GIST.Postcontrast CT shows the heterogeneously enhancing mass with intraluminal extension(arrow).胃肠间质瘤的转移途径 淋巴道转移：v到目前为止还没有文献有报道。v腺癌和淋巴瘤主要为淋巴道转移。v如果发现有淋巴结转移就应该考虑其他诊断。肠系膜转移v肠系膜转移通常见于肿瘤的复发，与术后腹膜种植相关。v也可与较大的小肠的间质瘤同时发现，胃的间质瘤较少见。v绝大多
16、数肠系膜的病灶为中心低密度。v因为病灶通常较小且远离原发病灶而漏诊。(Fig.10).v较大的病灶围绕肠系膜血管生长，但不引起远端机静脉栓塞。(Fig.11).Fig.10.76-year-old man with small-bowel gastrointestinal stromal tumor.Axial contrast-enhanced CT scan of mid abdomen shows rounded nodule(arrowhead)in mesentery in keeping with metastases.Metastasis is far from site of
17、resected tumor (arrow).Fifty-six-year-old male with GIST of the ileum.(a)Postcontrast CTshows 12 cm,partially necrotic primary tumour arising from the small bowel.(b)Three years later postresection of the primary tumour,peritoneal deposits are present in the right lower quadrant(arrow).Fig.11.75-yea
18、r-old woman with small-bowel gastrointestinal stromal tumor.Axial contrast-enhanced CT scan of mid abdomen shows large mesenteric mass(arrow)growing around mesenteric vessels(arrowheads).There is no thrombosis of mesenteric vessels.网膜转移v网膜转移较肠系膜转移更少见。v病灶通常直径小于2cm，均匀强化。v因为网膜是蠕动的，因此在下一次检查时可能不在同一个位置。v腹
19、水非常少见，多见于分子靶向治疗之后，由于药物纳税潴留副作用造成的。Fig.12.76-year-old man with small-bowel gastrointestinal stromal tumor.Axial contrast-enhanced CT scanaxial T2-weighted fat-suppressed fast spin-echo MRI(B)of pelvis show omental caking(arrows).肝转移v较小的肝转移瘤在治疗前表现为富血供。v增强CT上于门脉期表现为均匀明显强化；在肝静脉期完全排空(Fig.13)。v但是，在增强图像上并不是
20、所有的转移瘤同等程度强化，有的高密度，有的低密度，因为不是同一代的转移瘤(Fig.14)。Fig.13.78-year-old woman with small-bowel gastrointestinal stromal tumor.A,Axial breath-hold 3D fat-suppressed gradient-echo MRI of liver with gadolinium shows bright homogenous enhancement of metastasis(arrow)in late arterial phase.Smaller hypovascular m
21、etastases are also evident(arrowheads).B,In venous phase,MRI of large metastasis shows complete washout of contrast material(arrow).Smaller hypovascular metastases are also evident(arrowheads).Fig.14.50-year-old woman with gastric gastrointestinal stromal tumor.Axial contrast-enhanced CT scan of liv
22、er reveals hypovascular(arrow)and hypervascular(arrowhead)metastases.Other metastases.vLung metastases are extremely rare in GIST,even in the presence of extensive liver and peritoneal metastases.v这是与平滑肌肉瘤的一个很重要的鉴别点。v也没有明确的脑转移和骨转移的报道。ConclusionsvThe diagnosis of GIST can be suggested on imaging by t
23、he presence of a well-defined heterogeneously enhancing mass with necrotic center arising from the muscularis propria of the stomach or small bowel associated with a prominent extraluminal component。vGISTs are less frequently seen originating from the anorectum,colon or oesophagus.Metastases,if present occur in the liver or peritoneum.
