Malignant degree of gastrointestinal stromal tumor and the impact on biological behavior        HOU Ying-yong*, ZHU Xiong-zeng. *Department of Pathology，Zhongshan Hospital of Fudan University, Shanghai 200032, China
Corresponding author: HOU Ying-yong, E-mail: houyingyong@hotmail.com
Abstract    Tumor stage and grade for gastrointestinal stromal tumors are undetermined. Twelve 12 clinical and pathological parameters were identified. The parameters are classified into two gross spread parameters including liver metastasis and peritoneal dissemination, five microscopic spread parameters including lymph node metastasis, vascular, fat, nerve and mucosal infiltration, and five histological parameters including mitotic count > or =10 per 50 high-power fields, muscularis propria infiltration, coagulative necrosis, Chinese-ancient-coin-like pattern and severe nuclear atypia. Malignant gastrointestinal stromal tumors which presented at least one of  above-mentioned parameters can be divided into clinical stage I and II based on the absence and presence of gross spread respectively. The degree of malignancy of patients in clinical stage I could be graded according to the number of predictive parameters of malignancy. Patients in clinical stage II are of the highest degree of malignancy regardless of the number of parameters. It finds that the clinical stage and grade are associated with biologic behavior strongly.