ABSTRACT
Intraductal variant of peripheral cholangiocarcinoma is extremely rare. This variant shows intraductal growth and intraluminal extension without any infiltrative growth. The mode of intraductal growth is not known. The prognosis of this variant is better than that of usual cholangiocarcinoma. We report three cases, one of which is associated with Clonorchis sinensis (CS) infection. The tumors were entirely confined within the dilated peripheral tributaries of the intrahepatic bile duct. Microscopically, the tumors were well to moderately well differentiated, with a papillary or a micropapillary growth pattern. Focal clear cytoplasmic change and mucin production were noted. The tumors showed intraductal spreading without any invasion to the liver parenchyme. Mucosal hyperplasia and dysplasia were noted in the adjacent ducts. The authors assume that intraductal cholangiocarcinoma is a distinct subtype, and persistent irritation, such as, CS infection may undergo a malignant transformation through mucosal dysplasia.