Pancreatic acinar cell clusters in pediatric gastric mucosa.

Although clusters of pancreatic acinar cells (CPACs) have been reported in gastric mucosa of adults, they have not been described in children. We reviewed 283 pediatric gastric (239 antral and 44 corpus) mucosal biopsies during a 2-year period and detected CPACs in 10 antral biopsy samples. These biopsy samples were stained immunohistochemically for pancreatic exocrine markers (trypsin, chymotrypsin, alpha-amylase, and lipase) and a panel of regulatory substances (insulin, glucagon, somatostatin, pancreatic polypeptide, gastrin, and serotonin). Double immunostaining for colocalization of chromogranins and trypsin as well as mucin and trypsin also were performed on all cases. CPACs were seen in antral mucosa in a background of either normal or minimally inflamed mucosa, without any atrophy or metaplasia, and were positive for all pancreatic exocrine markers. Stray chromogranin-positive cells in the CPACs were also immunopositive for somatostatin, gastrin, or serotonin. All CPACs showed a few hybrid (amphicrine) cells that coexpressed both chromogranin and trypsin. In one case, ultrastructural examination showed such cells to contain both zymogen and neurosecretory granules. Although the presence of CPACs exclusively in the antrum is most likely the result of a sampling bias, the presence of hybrid cells with an amphicrine phenotype suggests that CPACs probably result from an aberration of stem cell differentiation.