Pedunculated Extraluminal Gastrointestinal Stromal Tumor of Stomach: A Rare Case Report in South Korea

Gastrointestinal stromal tumors (GISTs) are known to arise from any of the five layers of the gastric wall, most commonly from the muscularis propria. Extraluminal gastric GISTs account for approximately 8% of cases and are relatively rare, with pedunculated forms being scarcely reported in South Korea. A 25-year-old man presented to our hospital with an incidental left upper quadrant (LUQ) mass adjacent to the stomach on a screening computed tomography (CT) scan. He had no symptoms and no suspicious findings on gastrointestinal endoscopy. Laparoscopic excision was performed, revealing an 8 cm × 7 cm mass connected to the posterior gastric serosa. Immunohistochemical staining confirmed the diagnosis of GIST. We report this case as an extremely rare presentation of a gastric GIST presenting as a pedunculated mass connected to the outer serosal surface, underscoring the diagnostic challenges associated with such atypical presentations.