Mucin-producing bile duct carcinoma originating at the hepatic hilus

We describe a mucin-producing bile duct carcinoma that was resected and analyzed pathologically. Endoscopic retrograde cholangiography disclosed amorphous filling defects in the dilated extrahepatic bile duct, suggesting that a large amount of mucin was excreted from the tumor. An intraductal amorphous filling defect showed shape change at different examination times. Pathology examination revealed a papillary tumor which showed mucus production, in the right hepatic duct. The cut section of the resected specimen showed a protuberant papillary lesion, measuring 14×14mm in diameter, forming a cystic mucous lake within the duct wall. Many cancer cells were also found in the mucous lake, the contents of which were strongly positive for mucin stain. The mucous lake developed laterally and communicated with the peribiliary glands, suggesting that the tumor had originated in these glands.