Gastrointestinal stromal tumors: current diagnosis, biologic behavior, and management.

Gastrointestinal stromal tumors (GIST) are rare tumors of the gastrointestinal (GI) tract that arise from primitive mesenchymal cells. GISTs occur throughout the GI tract but are usually located in the stomach and small intestine. The majority of GISTs are immunohistochemically positive for c-kit protein (CD 117) and CD34. GISTs express a heterogeneous clinical course not easily predicted by standard pathological means. The most important prognostic factors are size > 5 cm, tumor necrosis, infiltration and metastasis to other sites, mitotic count > 1-5 per 10 high-powered fields, and most recently, mutation in the c-kit gene. Surgical resection remains the mainstay of treatment, as chemotherapy and radiation are ineffective. Long-term follow-up is imperative, as recurrence rates are high.