RÉSUMÉ
<p><b>OBJECTIVE</b>To investigate the clinicopathologic features of gastrointestinal stromal tumors (GISTs) and to identify reliable prognostic parameters.</p><p><b>METHODS</b>Fifty-nine GISTs were studied by immunostaining of CD117, CD34, SMA, desmin, S-100, bcl-2, and Ki-67. Histopathologic evaluations included tumor size, necrosis, histological growth patterns, mitotic activities and tumor lymphocytic infiltrate. The patients were clinically followed for 2 to 9 years. Univariate, multivariate and correlative statistical evaluations were used to analyze the data.</p><p><b>RESULTS</b>Among the 59 patients, 40 were alive and 15 died of their tumors at follow-up, the remaining 4 patients died of other causes. Pathological parameters that correlated with prognosis included tumor sizes of more than 5 cm, tumor tissue necrosis, mitotic cell count equal or higher than 5 per 50 high power field, Ki-67 labeling index (LI) equal or higher than 5% and intense bcl-2 immunostaining. Multivariate analysis showed that the mitotic count and Ki-67 LI were independent prognostic indicators. There was a correlation between mitotic count and Ki-67 LI.</p><p><b>CONCLUSIONS</b>Mitotic count and Ki-67 LI are the best predictors for a poor outcome of GIST after surgical treatment. Ki-67 immunostaining may substitute mitotic count as a useful prognostic parameter.</p>