Subepithelial tumors are frequently found in asymptomatic patients in Japan and Korea where cancer screening tests routinely include endoscopy. Most lesions are asymptomatic and clinically insignificant. However, carcinoid tumors, lymphomas, glomus tumor and gastrointestinal stromal tumors (GISTs) are malignant or have the potential to become malignant. Inflammation due to parasitic infestation by Anisakis and poorly differentiated adenocarcinomas in the stomach rarely present as subepithelial lesions. In contrast to the frequency of gastric GIST in the gastrointestinal system, they are uncommon in the duodenum and very rare in the esophagus. The prognosis of patients with GISTs in the stomach is relatively good compared with GISTs in other organs. Along with the location of the tumor, its size and mitotic count are major factors that determine the malignant potential of GIST. Small (<2 cm) asymptomatic GISTs usually have benign clinical course. GIST is the most common subepithelial tumor to occur in the stomach. Although various methods are employed to diagnose GISTs, the risk of GIST metastasis cannot be accurately predicted before lesions are completely resected. Recently, new endoscopic diagnostic methods and treatment techniques have been developed that allow the diagnosis and resection of lesions located in the muscularis propria, without any complications. These endoscopic methods have different indications depending on regions where they are performed.
Keywords: Endosonography; Gastrointestinal stromal tumors; Stomach neoplasms.