胃肠间质瘤影像学特点

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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

2、肿瘤表现为c-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 ce

3、lls. Appearance 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（

4、-）有助于协助鉴别诊断，S-100（-）可除外神 经源性肿瘤，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

5、低度恶性；直径25 cm 和5/50HPF 为低度恶性；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。,。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

6、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,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

7、, with heterogenous liver metastases.,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)。 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 pelvi

8、s shows exophytic heterogeneously enhancing 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).,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

9、. 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

10、male with GIST of gastric fundus. Postcontrast CT shows 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 intralumi

11、nal component of tumor with pocket of gas (arrow).,B, In 63-year-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 gastrointestina

12、l stromal tumor.,B). This tumor was originally mistaken for infected 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.,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。(Fi

13、g. 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-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

14、) 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 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

15、. (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。

16、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