A MUCOUS NECK CELL ADENOMA OF THE DUODENAL BULB ARISING FROM ECTOPIC GASTRIC MUCOSA—A CASE REPORT

Abstract

A 77-year-old man was detected with a 2-cm submucosal tumor (SMT)-like lesion in the duodenal bulb. The lesion had a depression on its surface. Endoscopic ultrasonography revealed that it was a submucosal tumor. However, because this lesion was soft and movable without erosions and ulcerations, we assumed it to be intramucosal and performed endoscopic mucosal resection. Histological examination of the resected specimen revealed that the tumor cells resembled those in Brunner's gland adenoma. Immunohistochemical findings were positive for pepsinogen-I, MUC6, and CDX2 and partially positive for H+/K+-ATPase, MUC5AC, and CD10. These staining characteristics were consistent with those of mucous neck cells and primitive chief cells of the fundic glands. In addition, a gastric-to-intestinal transition was indicated by CDX2 and CD10 expression. A diagnosis of mucous neck cell adenoma of the duodenal bulb arising from ectopic gastric mucosa was made. To the best of our knowledge, this is the first reported case of a duodenal bulb adenoma arising from ectopic gastric mucosa and comprising fundic gland cells (mucous neck cells).