Fig. 4

Representative images with pathological findings. a A pedunculated polyp (14 × 11 × 15 mm) was observed in the neck of the gallbladder (arrow), the gallbladder wall was thickened, and Rokitansky-Aschoff sinus (RAS) could be observed clustered in the wall. b The polypoid lesion comprised solid or trabecular nests of NET cells. These tumor cells had multivacuolated clear cytoplasm (hematoxylin and eosin staining, × 40 magnification). Immunohistochemically, the tumor cells were positive for synaptophysin (c) and chromogranin A (d)