Mucus retention in heterotopic pancreas of the gastric antrum. A lesion mimicking mucinous carcinoma.

This report describes mucus retention developing in heterotopic pancreas of the gastric antrum. This unusual complication of heterotopic pancreas was seen in a 54-year-old black man who presented with postprandial nausea, vomiting, and weight loss. Gastroscopy revealed a 2-cm pyloric polyp, which was seen to intermittently obstruct the pylorus. Exploratory laparotomy confirmed an intramural mass in the antrum with serosal thickening and nodules. Frozen-section examination of the serosal nodule revealed a pool of mucus containing epithelial clusters and chronic inflammatory cells with no verifiable pancreatic tissue. These findings suggested the possibility of a mucinous carcinoma involving the serosa. Following gastrectomy, however, heterotopic pancreatic tissue was identified in the outer muscular propria extending to the mucosa of the antrum with no evidence of carcinoma. This heterotopic pancreatic tissue showed ductal obstruction and mucus retention. As a result, some ducts were ruptured and transformed into small nodules of mucus lakes with clusters of residual ductal epithelium. We therefore concluded that the mucous extravasation nodules on the antral serosa represented a benign lesion resulting from mucus retention in the heterotopic pancreas. In contrast to mucinous carcinoma, these benign mucous extravasation nodules were closely associated with the heterotopic pancreas, and showed significant inflammation and fibrosis but no overt epithelial anaplasia. The significance of the mucous extravasation nodule in the heterotopic pancreas is its potential confusion with mucinous carcinoma.