Gastrointestinal stromal tumors (GISTs)are the most common mesenchymal neoplasms of the gastrointestinal tract. When making treatment plan it is very important to make proper tumor aggressiveness estimation. Traditionally, the best prognostic factors are tumor size and number of mitoses. The aim of this study was to define which GIST classifica- tion (Amin’s or Newman’s classification or Fletcher’s Consensus Criteria) is the most significant determining prognosis and has the strongest impact on survival. This study included 63 GIST patients whose tumor specimens were evaluated by standard histopathological methods and classified based on histological assessment of malignant behavior to the three different systems. Comparison of those classification systems was done and none of them was proven to be statisti- cally significantly better in predicting overall survival and probability of lethal outcome. We conclude that all three clas- sifications are comparable in prediction of malignant behavior. The worst prognostic factor is existence of metastases at the time of disease diagnosis
