Fig. 4

Macroscopic and microscopic findings of resected specimen. a Resected specimen showing a papillary tumor in the cystic wall. b–d Histopathological examination revealed the presence of an intraductal papillary neoplasm of the bile duct on hematoxylin and eosin (H&E) staining. b The papillary tumor cells (black arrow) can be observed in the cystic wall (white arrow) (H&E staining; magnification, × 40). c The tumor was a high-grade (H&E staining; magnification, × 400). d The tumor only located in the cystic wall and did not invade the wall of the adjacent bile duct (H&E staining; magnification, × 400)