An Adult Gastric Duplication Cyst Mimicking a Gastrointestinal Stromal Tumor

We herein describe a rare case of a 24-year-old man who presented with severe epigastralgia after consuming a considerable amount of broiled meat. Computed tomography revealed a cystic lesion adjacent to the distal stomach, with high intensity on T2-weighted magnetic resonance imaging. Upper endoscopy showed a cystic mass measuring 6 cm in diameter, mimicking a submucosal tumor adjacent to the pyloric valve, with duodenum invagination, characteristic of ball valve syndrome. Endoscopic ultrasonography showed that the lesion was contiguous through the first to the third layer of the stomach. Therefore, we performed distal gastrectomy. Pathology showed that the lesion was a gastric duplication cyst without malignancy.