Abstract
A 63-year-old man underwent distal pancreatectomy for intraductal papillary mucinous neoplasm (IPMN) 2 years previously and was being followed-up. Although the patient had no specific symptoms, a submucosal tumor 2 cm in diameter was detected on upper gastrointestinal endoscopy in the middle portion of the gastric corpus during a health checkup. A detailed examination could not completely rule out the likelihood of the tumor being associated with malignant disease. Thus, partial gastric resection was performed. Histopathological examination of the resected specimen revealed no tumor in the gastric mucosa, but a highly well-differentiated intestinal type adenocarcinoma was confirmed in the part of the mucosa between the fundic gland and the pyloric gland. The tumor showed cystic dilatation distributed in the submucosal layer of a hamartomatous inverted polyp (HIP). Thirty-one cases of HIP have been reported in Japan, including this case. Of these, concomitant gastric cancer was confirmed in 4 cases including this one, but cancer in the mucosa showing cystic dilatation was seen only in our case. Treatment strategies need to be decided after considering the possibility of malignant disease in cystic lesions in the submucosal layer of an HIP.
