Prognostic impact of blood vessel invasion in gastrointestinal stromal tumor of the stomach

Gastrointestinal stromal tumors have a wide spectrum of biologic behavior, and occasional cases show liver metastases. The modified risk grade based on tumor size and mitotic counts has been proposed to predict the biologic behavior in gastric gastrointestinal stromal tumors. Blood vessel invasion (BVI) is important in the development of metastasis of various kinds of cancer. The aim of this study was to elucidate the potential role of blood vessel invasion in gastric gastrointestinal stromal tumors. Blood vessel invasion was found in 17 of 122 cases (13.9%) of gastrointestinal stromal tumors, and was significantly correlated with larger tumor size, higher mitotic count and higher modified risk grade. Among 83 cases of primary, localized gastric gastrointestinal stromal tumors available for follow-up information, liver metastasis was observed in 14 cases (16.9%). When blood vessel invasion was positive in the primary tumor, liver metastasis occurred in 80% of cases after the initial surgery, indicating that blood vessel invasion was a significant risk factor of liver metastasis (P < .0001). In univariate and multivariate analyses, tumor size (>5 cm), mitotic count (>5/50 high-power fields) and blood vessel invasion (positive) were significantly associated with a shorter period of disease-free survival. Our results suggest that the evaluation of blood vessel invasion may be useful for predicting the risk of liver metastasis and aggressive biologic behavior of gastrointestinal stromal tumors, and may serve as important information for determining the therapeutic strategies including adjuvant molecular target therapy.