<prompt> what is the marker most predominant in gastrointestinal tumor is ?CD 117CD 34CD 56CD 24  <response>: Pathophysiology Tyrosine kinase receptor mutations in GIST Over 85 of GISTs have activating KIT mutations Commonly occur in Exon 1157-71 Exon 9 10-18 Exon13 1-4 Exon 171-4 One third of GISTs lacking KIT mutations have mutations in gene encoding PDGFRA, Mutated KIT remain active in the absence of ligand binding resulting in unregulated growth and malignant transformation Wild type GISTs are few that do not show KIT or PDGFRA mutations Surgical therapy Complete en-block removal Site specific Avoidance of tumor rupture Lymphadenectomy not advocated Final goal: complete tumor resection with a negative margin, intact pseudocasule Positive resection margin: Re-excision REF : BAILEY AND LOVE 27TH ED 