A 50 Yr. old male presents with obstructive symptoms. Biopsy of stomach reveals Gastrointestinal stromal tumor (GIST). Most appropriate marker for GIST is

.* GIST arises from interstitial cell of Cajal (pacemaker cell which intercalates between smooth muscle cells and intramural neurons). Mutation of tyrosine kinase and platelet derived growth factor alpha (PDGFa) are the newer pathogenetic theories. * GIST is classified as very low risk (2 cm); low risk (2-5 cm); intermediate risk (5-10 cm) and high risk (> 10 cm) based on tumour size and mitotic activity of cells. * 95% of GISTS express c-kit - CD117 mutations - a specific molecular marker. ref:SRB&;s manual of surgery ,ed 3,pg no 791