Fig. 5

Histopathological examination. A Macroscopic findings. The resected specimen revealed a 15-mm white nodule within the submucosa of the duodenum (white triangle). B Hematoxylin and eosin stain. The tumor (white triangles) was limited to the submucosa of the duodenum and separated from the pancreatic tissue (black arrows) by the duodenal muscularis (white arrows). C Hematoxylin and eosin stain which the enlargement of the black square in B. Tumor cells were not detected within the pancreatic duct around the tumor, and the duct was considered the accessory pancreatic duct (black triangles). D Hematoxylin and eosin stain at the adjacent section. Normal pancreatic tissue (striped arrows) was observed in the accessory papilla region of the duodenum, which sat in a semicircle around the tumor (white triangles). This normal pancreatic tissue was separated from the pancreatic parenchyma (black arrows) by the duodenal muscle layer (white arrows) and thus considered as pancreatic tissue in the accessory papilla region. E Hematoxylin and eosin stain which the enlargement of the black square in D. At high magnification, acinar cells (striped arrows) and islets of Langerhans (striped triangles) were seen next to the tumor (white triangles)