1、胃肠间质瘤(GIST)2009-01-01 杨梅 流行病学特点 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。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 the GIST cells are closely related to the interstitial cells of Cajal(ICC)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。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 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.Appea
3、rance on H and E stain is similar to that of smooth muscle tumor.免疫组化检查 The 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.。另外，CD34（+），S-100（-），GFAP（-）有助于协助鉴别诊断，S-100（-）可除外神 经
4、源性肿瘤，GFAP（-）可除外胶质瘤。临床特点 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。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。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）Fletcher 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；直径5
5、10 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。Chiappa 等3报道胃肠间质瘤术后复发或转移的时间是436 个月。个别报道时间长达十几年。临床症状 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。肿瘤出血是由于溃疡所致。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。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Vater壶腹部。钡餐检查
6、 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 边界清晰不均质的肿块 边缘强化明显，厚度不均，中心密度减低。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 metastases.很多肿瘤发现时
7、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)。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。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。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 enhancing mass(arr
8、ow).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).偶尔也会在CT上发现腔内的肿瘤(Fig.4).。口服造影剂时可发现粘膜下溃疡(Fig.5)。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)。肿瘤与肠管壁常仅通过一个很薄的蒂相连，要认真辨认
9、肿瘤的起源。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 shows homogenous intr
10、aluminal 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-year-old woman with
11、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 pancreatic pseudo
12、cyst.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.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).原因：肿瘤迅速生长。肿瘤破坏肌间神经丛。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-old man with small-bo
13、wel 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。Seventy-seven-year-old
14、male with GIST of the ileum.Postcontrast CT shows a large intra-abdominal mass with central cavitation.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 CT shows 12 cm,partially necrotic primary tumour arising from the small bowel.直肠结肠的间质瘤表现为边界清
15、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：到目前为止还没有文献有报道。腺癌和淋巴瘤主要为淋巴道转移。如果发现有淋巴结转移就应该考虑其他诊断。肠系膜转移 肠系膜转移通常见于肿瘤的复发，与术后腹膜种植相关。也可与较大的小肠的间质瘤同时发现，胃的间质瘤较少见。绝大多数肠系膜的病灶为中心低密度。因为病灶通常较小且远
16、离原发病灶而漏诊。(Fig.10).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 resected tumor (arrow).Fifty-six-year-old male with GIST of the ileum.(a)Postcontrast CT shows 12 cm,partially necrotic primary tumour arising from the small bowel.(b)Three years later postresection of the primary tumour,perit
