Ectopic Tissue Consisting of a Mixture of Glandular Gastric, Intestinal, and Exocrine Pancreatic Tissue in the Forestomach of a Rat

The development of ectopic gastric, intestinal, or pancreatic tissue in the gastrointestinal tract is extremely rare in rats, although it is fairly common in humans. In this report, we describe an unusual case in which a mixture of different types of ectopic tissue was found in the forestomach of a rat. A solitary white nodular/polypoid structure, which measured 5 mm in size, was detected on the luminal surface of the greater curvature of the forestomach in an 8-week-old female Crl:CD(SD) rat. A histological examination revealed that the lesion contained ectopic glandular gastric tissue, including gastric surface mucous cells, parietal cells, and pyloric gland cells, which was confirmed by immunohistochemistry. Moreover, the lesion also contained villin-positive columnar intestinal absorptive cells and chymotrypsin-positive pancreatic exocrine tissue. To the best of our knowledge, this is the first study to detect a mixture of ectopic glandular gastric, intestinal, and exocrine pancreatic tissue in a rat.