Tumor necrosis and >20 mitoses per 50 high-power fields can distinguish 'very high-risk' and 'highest-risk' within 'high-risk' gastric gastrointestinal stromal tumor.

AIM: We aimed to investigate the optimal criteria for classifying higher risk forms of gastric gastrointestinal stromal tumor (gGIST).

MATERIALS & METHODS: A total of 246 high-risk gGIST patients were enrolled. Univariate and multivariate analyses were conducted to determine the association between clinicopathological features and overall survival. Appropriate cut-off values were calculated to identify those at higher risk of gGIST.

RESULTS: Multivariate and univariate analyses revealed that tumor necrosis and mitotic counts are independent risk factors for overall survival. The optimal cut-off value of mitotic counts was 20. Patients with both necrosis and >20 mitoses/50 high-power fields were worse than those with either one.

CONCLUSION: Tumor necrosis and >20 mitoses/50 high-power fields are independent risk factors for high-risk gGIST. Patients with both risk factors indicate worse prognosis.