page_title: Gastrointestinal stromal tumor
section_title: Imaging
hierarchical_section_title: Gastrointestinal stromal tumor / Diagnosis / Imaging
caption_attribution_description: Русский: КТ-скан небольшой субсерозной ГИСО, исходящей из задней стенки желудкаEnglish: Axial CT image of a small subserous gastrointestinal stromal tumor in the posterior wall of the stomach
context_page_description: Gastrointestinal stromal tumors are the most common mesenchymal neoplasms of the gastrointestinal tract. GISTs arise in the smooth muscle pacemaker interstitial cell of Cajal, or similar cells. They are defined as tumors whose behavior is driven by mutations in the KIT gene, PDGFRA gene, or BRAF kinase. 95% of GISTs stain positively for KIT. Most occur in the stomach and gastric GISTs have a lower malignant potential than tumors found elsewhere in the GI tract.
context_section_description: The purpose of radiologic imaging is to locate the lesion, evaluate for signs of invasion and detect metastasis. Features of GIST vary depending on tumor size and organ of origin. The diameter can range from a few millimeters to more than 30 cm.  Larger tumors usually cause symptoms in contrast to those found incidentally which tend to be smaller and have better prognosis. Large tumors tend to exhibit malignant behavior but small GISTs may also demonstrate clinically aggressive behavior.
  Plain radiographs are not very helpful in the evaluation of GISTs. If an abnormality is seen, it will be an indirect sign due to the tumor mass effect on adjacent organs. On abdominal x-ray, stomach GISTs may appear as a radiopaque mass altering the shape of the gastric air shadow. Intestinal GISTs may displace loops of bowel and larger tumors may obstruct the bowel and films will show an obstructive pattern. If cavitations are present, plain radiographs will show collections of air within the tumor. Calcification is an unusual feature of GIST but if present can be visible on plain films.
  Barium fluoroscopic examinations and CT are commonly used to evaluate the patient with abdominal complaints. Barium swallow images show abnormalities in 80% of GIST cases. However, some GISTs may be located entirely outside the lumen of the bowel and will not be appreciated with a barium swallow. Even in cases when the barium swallow is abnormal, an MRI or CT scan must follow since it is impossible to evaluate abdominal cavities and other abdominal organs with a barium swallow alone. In a CT scan, abnormalities may be seen in 87% of patients and it should be made with both oral and intravenous contrast.  Among imaging studies, MRI has the best tissue contrast, which aids in the identification of masses within the GI tract (intramural masses). Intravenous contrast material is needed to evaluate lesion vascularity.
  Preferred imaging modalities in the evaluation of GISTs are CT and MRI, and, in selected situations, endoscopic ultrasound. CT advantages include its ability to demonstrate evidence of nearby organ invasion, ascites, and metastases. The ability of MRI to produce images in multiple planes is helpful in determining the bowel as the organ of origin (which is difficult when the tumor is very large), facilitating diagnosis.
caption: Non-enhanced CT image of a small GIST in the posterior stomach wall (arrow).  The lesion appears subserosal. Incidental finding.
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