Primary duodenal carcinoma suspected to arise from ectopic gastric mucosa: a case report

BACKGROUND: Ectopic gastric mucosa mainly occurs in the duodenal bulb, and its etiology is thought to be congenital straying of gastric tissues. Primary duodenal carcinoma is a rare disease; however, reports of carcinoma arising from ectopic gastric mucosa are extremely rare. We report a case of primary duodenal carcinoma suspected to arise from ectopic gastric mucosa, which discovered as a result of duodenal stenosis. CASE PRESENTATION: The patient was a 71-year-old man with persistent weight loss and white stools. Enhanced computed tomography showed stenosis of the third portion of the duodenum and main pancreatic duct dilatation. Upper gastrointestinal endoscopy revealed irregularity of the duodenal mucosa from the anorectal side of the papilla of Vater to the stenosis of the third portion. No malignant cells were found by biopsies from the duodenal mucosa. Endoscopic ultrasonography did not detect the tumor in the pancreatic head. The possibility of a pancreatic tumor could not be ruled out based on findings of main pancreatic duct dilatation in the pancreatic head, and the patient had long-term poor oral intake because of duodenal stenosis; thus, surgical treatment was planned. Intraoperative findings showed palpable induration of the third portion of the duodenum and white nodules on the serosal surface. This was diagnosed as primary duodenal carcinoma, and pylorus-preserving pancreatoduodenectomy was performed. Histopathological diagnosis revealed ectopic gastric mucosa in the papilla of Vater and well-differentiated tubular adenocarcinoma invaded the normal duodenal submucosa and extended to the duodenal serosa. No mass lesion was detected in the pancreas, and an intraductal papillary mucinous neoplasm was observed in the branch pancreatic duct. The main pancreatic duct stricture was caused by the duodenal carcinoma invasion. CONCLUSIONS: This case of primary duodenal carcinoma was suspected to arise from ectopic gastric mucosa and review the relevant literature.