Fig. 3 .

a. Nonneoplastic heterotopic pancreatic tissue (arrow) was present within the submucosal and proper muscular layer of the duodenum. 3b. Heterotopic pancreatic tissue is composed of complete structures consisting of ducts (arrowhead), acini (white arrow), and islets of Langerhans cells (arrow) (Heinrich classification; Type I). 3c. Direct transitions between the normal pancreatic structures (arrow) and the carcinoma (arrowhead) were observed. 3d. The histological type was moderately differentiated tubular adenocarcinoma.