[A case of an adenocarcinoma in a duplication cyst of the esophagogastric junction].

Duplication cysts of the esophagogastric junction are an extremely rare disease entity. Computed tomography showed a cystic lesion in the wall of the esophagogastric junction ofa 75-year-old man. The cystic tumor gradually increased in size from 40 mm to 60 mm in diameter within 6 months. On the basis of magnetic resonance cholangiopancreatography and positron emission tomography, it was described as a cystic pathological alteration enclosing a solid lesion. The pre-operative diagnosis was a gastrointestinal stromal tumor in the stomach cardia, and we performed proximal gastrectomy under laparotomy. Histological findings showed gastric mucosa in the internal mucosa of the cyst and an adenocarcinoma inside the cyst. We diagnosed the cystic tumor as a duplication cyst of the esophagogastric junction with adenocarcinoma. It is important to carefully choose the procedure to be used for resection of cystic tumors adjacent to the alimentary canal.