Introduction: Gastrointestinal stromal tumors (GIST) are the most common mesenchymal neoplasms of the gastrointestinal system. The tumor arises from the middle layer of the gastrointestinal epithelium and can develop in the body organs such as esophagus, stomach, small intestine, colorectal, or mesenteric… Histopathological examination takes an important part in confirming the GIST, in oder to choose an appropriate therapeutics for the patients. This study aims to explore the clinicopathological characteristics and evaluated the relationships between malignant risk classification according to Armed Forces Institute of Pathology criteria and the clinicopathological features of GISTs in a cohort of Vietnamese patients. Methods: Eighty-nine patients with primary GIST who underwent surgery with primary curative intent between 2014 and 2019 at Hue Central Hospital, Vietnam. We evaluated the clinicopathological characteristics and immunohistochemical findings of all patients. Results: The average age was 55.9 ± 11.9. The size of tumor >
2 - 5cm was accounted for 64.1%. The most common position was at the stomach as 48.5%. Type of rhombus cells occupy the majority of patients as 85.9%. Type of epithelial form was 10.9 %. Type of multi-morphology was seen in 1 case (3.2%). All samples was positive with CD117, followed by Vimentin positive with a significant rate of 97.4%, CD34 positive 61.5%, no case positive for Desmin. High-risk GIST dominant 46.9%, followed by the intermediate risk GIST occures 28.1%, low-risk GIST in 2 to 0.3%, still a very low risk GIST with 4.7%. There was a significant correlation between the factors tumor necrosis with tumor size, tumor necrosis with the number of multiplication, mucosal infiltration with size of the tumor. Conclusions: There was a significant association between the risk level according to AFIP criteria and the necrosis or mucosal invasion of the tumor