Gastrointestinal stromal tumor - A study of 158 cases: Clinicopathological features and prognostic factors

OBJECTIVE: To increase knowledge on the behavior of gastrointestinal stromal tumors (GISTs) and factors influencing therapy. STUDY DESIGN. The clinicomorphological features of 158 GISTs were analyzed. Survival analysis was performed on the whole series, as well as on a selected group of patients with high risk GIST who did not receive imatinib mesylate. The impact of imatinib mesylate on the prognosis was investigated. RESULTS: Most of the GISTs had a benign behavior. The risk class was a powerful prognostic factor but was unable to predict the outcome in a single case; even patients in the high risk class not receiving imatinib mesylate had a low mortality rate. In this group, it was the mitotic activity that better correlated with prognosis, and a cut point of 10 mitoses per 50 high-power field can be fixed to discriminate cases with favorable or unfavorable outcome. Patients with GISTs presenting as aggressive disease received great benefit from imatinib mesylate therapy. CONCLUSION. Mitotic activity is important in predicting the outcome of patients with high risk GIST who present at diagnosis without dissemination. This finding can have therapeutic implications.