Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract, with an annual incidence of 12 to 14 per million persons.1
The tumors are found in the stomach (52%), small intestine (25%), colon (11%), esophagus (5%), and rectum (2%), as well as in the omentum, mesentery, and peritoneum.2
The cellular origin of GISTs is thought to be the interstitial cells of Cajal (ICC), the intestinal pacemaker.3
GISTs appear histologically similar to leiomyosarcomas of the GI tract but are positive for the immunohistochemical marker for the KIT protein (CD117).4
The tumors occur in three histologic variants: spindle cell type (70%), epithelial type (20%), and combined spindle cell-epithelial type (10%).
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