Gastrointestinal Stromal Tumors (GIST)
Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor of the gastrointestinal tract, and the majority of GISTs express the Kit receptor (stem cell factor receptor, CD117), as shown by immunohistochemical analysis. GISTs account for approximately 2% of all stomach cancers, 14% of all small intestine tumors, and 0.1% of colon cancers, with an annual incidence of approximately 20 cases/million inhabitants. The median age at diagnosis is around 58 years. In the 1940s, GISTs were often diagnosed as smooth muscle tumors of the GI tract (GI leiomyosarcoma, leiomyoblastoma, and leiomyoma), but advances in histopathology later provided ultrastructural evidence that GISTs were distinct from smooth muscle tumors.