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.