An 80-year-old woman presented with an asymptomatic, painless lump in the right breast. Positron emission tomography incidentally revealed a 45 mm × 25 mm-sized, dumbbell-shaped mass in the epigastric region. Abdominal computed tomography showed that the mass was adjacent to both the stomach and the small intestine. Endoscopic ultrasonography (EUS) showed that the hypoechoic mass had a 1.6 mm-diameter stalk attached to the 4th layer of the gastric wall. Laparoscopic partial gastrectomy was performed. The gastric mass with a narrow stalk was resected and was confirmed as GIST of the stomach histopathologically. The stalk of this tumor was composed of smooth muscle tissue without tumor cells. The diameter of the stalk was 1.6 mm on EUS, and 2.2 mm on histopathological examination. We believe that in vivo in some extra-luminal pedunculated gastric GISTs the stalk may become longer and thinner as the GIST grows.
