The GIST paradigm: how to establish diagnostic and prognostic criteria.

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.