Imaging of gastrointestinal stromal tumor

Gastrointestinal stromal tumor (GIST) is a rare stromal neoplasm that accounts for 5% of all soft tissue sarcomas.1 It is the most common mesenchymal neoplasm of the gastrointestinal tract. Before the advent of immunohistologic methods, most spindle cell sarcomas of the gastrointestinal tract were considered to be leiomyomas or leiomyosarcomas, with occasional examples of neurogenic tumors. GIST defines a distinct group of gastrointestinal tumors that originate from the intestinal cells of Cajal. These cells act as regulators of bowel peristalsis and therefore are also called pacemaker cells. Cajal cells normally express cKIT (CD 117), which is a tyrosine kinase growth factor receptor. This cKIT immunoreactivity is the best defining feature of GISTs, distinguishing them from true smooth muscle tumors (i.e., leiomyomas and leiomyosarcomas) and tumors arising from neural crest derivatives (i.e., schwannomas and neurofibromas); this is considered the most specific criterion for the diagnosis of GIST. In addition, targeting the cKIT receptor with a cKIT tyrosine kinase inhibitor [STI-571, imatinib (gleevec); Novartis, Basel, Switzerland] has been successfully utilized in treating patients with GIST