Surgical outcomes and immunohistochemical features for gastrointestinal stomal tumors (GISTs) of the stomach: with special reference to prognostic factors

Background/Aims: Stomach is the most common site of gastrointestinal stromal tumors (GISTs). But the preoperative pathologic diagnosis is often difficult to make and it is hard to decide an appropriate surgical extent and also adjuvant therapy due to obscure malignant potential. Our purpose was to observe the outcomes for the patients with GIST of the stomach and reveal the significant prognostic factors. Methodology: Forty patients operated for primary GIST of the stomach expressing CD 117 were studied. We evaluated immunohistochemical and clinicopathologic features, and analyzed them to reveal the significant prognostic factors. The surgical outcomes of the patients were also investigated. Results: Multivariate analysis for disease-free survival disclosed mitotic activity was the only independent factor, but the immunohistochemical features did not have any prognostic value. Among the patients with recurrence, all of the patients treated with imatinib mesylate (formerly STI-571) have survived until now, but half of the untreated patients died. Conclusions: In gastric GISTs, most important prognostic factor is mitotic count, not tumor size. We suggest that the wider application of imatinib mesylate to clinically malignant gastric GIST as adjuvant therapy may contribute to the improvement of outcomes.