Gastrointestinal stromal tumor
Gastrointestinal stromal tumor (GISTs) are a non-epithelial mesenchymal neoplasms of the canine cecum, large intestine and stomach.
These tumors are less common than gastric carcinoma but have been reported in the dog. They are thought to arise from interstitial cells of Cajal or their stem cell precursors which are normally part of the autonomic nervous system of the intestine, serving as a pacemaker in controlling gastric motility.
Gastrointestinal stromal tumors can also develop outside the intestinal tract, within the abdominopelvic cavity such as the omentum, mesentery, uterus, and the retroperitoneum; they are called extragastrointestinal stromal tumors (eGIST) and usually behave aggressively.
Clinical symptoms are those similar to gastric carcinomas and include dysphagia, vomiting, anorexia and weight loss.
Barium meal may reveal irregularities of the gastric mucosa, and endoscopy may reveal gastric mucosal thickening and reddening (ulcerations are rare) and stenosis or narrowing at the pyloric antrum.
Diagnosis usually requires histopathological analysis of biopsied material obtained during endoscopy or gastrotomy. Highly differentiated cell with a high mitotic index infers a poorer prognosis in most cases.
Definitive diagnosis requires the demonstration of the expression of KIT (CD117), a type III tyrosine kinase receptor encoded by the proto-oncogene c-KIT, although a small proportion of GISTs do not exhibit CD117 immunoreactivity.
Fortunately, with the recent advancement of proto-oncogene testing and immunohistochemical staining, treatment for GIST has improved with gene therapy directed against specific kit/PDGFRA proto-oncogene, showing promising results.
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