A 42-year-old woman with 2-day history of acute onset severe epigastric pain, nausea, and vomiting presented to our emergency department. She had no previous significant cardiovascular or gastrointestinal diseases. Her vital signs were stable. Physical examination revealed that mild tenderness of her epigastrium without guarding or rebound tenderness. Laboratory findings showed no abnormalities. Abdominal computed tomography (CT) showed diffusely thickened gastric wall (Fig. A). What is most likely diagnosis?
