Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the gastrointestinal tract. The present review evaluates the most important parameters in GIST: epidemiology, principal clinical presentations, histopathological patterns of GIST with differential diagnosis and Fletcher's and Miettinen's risk classification, immunohistochemistry, prognostic factors, c-KIT and PDGFRalpha mutations and treatment of this tumor. The most frequent site for GISTs is the stomach, followed by the duodenum and small intestine; spindle cell morphology is described in 70% with CD17 positivity in around 95% of the cases; exon 11 of c-KIT is the most mutated, with Gleevec being the principal treatment. In GISTs, high mitotic rate, large tumor size, incomplete resection, extragastrointestinal site, duplication 502-503 in exon 9 of c-KIT, and secondary mutations are negative prognostic factors.