Q) True statement regarding GIST is  (AIIMS 2019)

a) 80% of GIST arise from stomach

b) ILeal GIST is resistant to Imatinab

c) Leiomyosarcomas do not express CD 117

d) Prognosis of GIST does not depend on the site of lesion 

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 They can appear anywhere within the GI tract, although they are usually found in the stomach (40% to 60%), small intestine (30%), and colon (15%).
 Development of imatinib mesylate has significantly altered previous treatment strategies. Imatinib mesylate is a tyrosine kinase inhibitor that blocks the unregulated mutant c-kit tyrosine kinase and inhibits the BCR-ABL and PDGF tyrosine kinases.
Current guidelines suggest that patients with high-risk disease should receive 3 years of adjuvant  therapy at all sites
Sabiston page 1280
Ileal GIST are more malignant than stomach GIST


Among the gastric tumors, there were no examples of true leiomyosarcomas, whereas there were four small intestinal, four colonic, and two rectal tumors that histologically showed features of differentiated smooth muscle cells with blunt-ended nuclei and eosinophilic, sometimes granular, cytoplasm. These tumors were, by definition, all positive for SMA, and seven also were positive for desmin. Although all leiomyosarcomas were generally negative for CD117, scattered large neoplastic spindle cells (less than 1% of tumor cells) in two intestinal leiomyosarcomas showed strong cytoplasmic positivity; these four tumors were negative for CD34.