Gastrointestinal stromal tumors (GIST) represent rare malignancies of mesenchymal origin that can appear at any site of the gastrointestinal tract. Their classification, patient treatment and prognosis had been a source of controversy. The biology of these tumors revealed association to the type III tyrosine kinase receptor and the KIT CD117 protein expression. GIST mesenchymal lesions derive from the interstitial cells of Cajal. Classification methods include the one by Miettinen and Lasota and the ‘‘modified NIH classification’’. The treatment of choice is surgical intervention and complete removal of the neoplasm. In patients with tumors that cannot be excised, have given metastasis, or are of high risk for metastasis, treatment also involves Kit/PDGFRA tyrosine kinase inhibitors, such as imatinib. In Greece, several cases have been described.