Fig. 6

Pathological findings. a Hematoxylin-eosin (HE) staining indicated tumor cells were localized in the bile duct and no infiltration into the hepatic parenchyma was observed. *: bile duct lumen. b Atypical proliferation of cells with enlarged nuclei and exhibiting irregular ductal structures. Immunohistochemical staining revealed that the tumor cells were positive for CK-7 (c) and WT-1 (e), and negative for CK-20 (d)