Gastrointestinal stromal tumor (GIST) is the most common mesenchymal neoplasm of the gastrointestinal tract, if not the most common sarcoma overall (Reichardt et al. 2009). GIST is believed to arise from the interstitial cells of Cajal or their precursors. These pacemaker cells of the bowel have features of smooth muscle cells, fibroblasts, and neurons to various degrees (Huizinga et al. 1995).
GIST characteristically stains positive for the KIT receptor tyrosine kinase by immunohistochemistry. At the genomic level, mutations in KIT or the receptor tyrosine kinase PDGFRA are the hallmark of this diagnosis (Hirota et al. 1998). KIT and PDGFRA are mutated in ~85% and ~5%, respectively, of GIST. Mutations are also rarely found in the serine-threonine kinase, BRAF (<1%) (Figure 1).
The incidence of GIST is on the order of 10–15/million (3000–4500 cases/year in the US) (Nilsson et al. 2005), although autopsy series may identify as many as 10% of people examined with microscopic GIST.
Figure 1. Molecular subsets of GIST.
Last Updated: June 1, 2012
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