Gastrointestinal stromal tumor (GIST) are the most
common non-epithelial neoplasms of the gastrointestinal tract (GIT), despite mesenchymal
cancers contribute only 1% of primary GI malignancy (Miettinen 1999). Annual
incidences of GIST in the United States (US) is about 4000-6000 cases, commonly
seen in adults aged over 40. Generally, there is no specific gender
predilection, although some studies reported slight male preponderance (Miettinen 2005; Tryggvason 2005; Kawanowa 2006). GISTs are
thought to arise from interstitial cells of Cajal, a pleuripotent mesenchymal
stem cells that acts as a pacemaker for bowel motility. HPE of GIST specimens
usually show atypical spindle cells with 95% of cases express the receptor
tyrosine kinase KIT protein (also
widely known as CD117) on immunohistochemistry (Hirota 1998; Kindblom 1998).
The availability of Imatinib mesylate (GlivecÒ) has
revolutionized the GIST treatment in recent years. The drug selectively
inhibits the tyrosine kinase and prevents cell proliferation. The recognition
of mutational activation of the KIT or PDGFRA genes stimulated the growth of
these cancer cells led to the development of this effective systemic therapy.