[Cancer arising in choledochal cyst and management].

Biliary cancer develops in 20-30% of the patients with choledochal cyst and pancreatobiliary malunion. Some bile acid fractions and refluxed pancreatic enxymes into the bile duct is probably responsible for carcinogenesis. Cancer often develops in the extrahepatic bile duct and gallbladder, and rarely in the intrahepatic duct. In cystic dilatation, cancer often occurs in the common bile duct, while in diffuse or non-dilated type it occurs in the gallbladder. Cancer usually occurs in younger patients than does biliary cancer in general population, and the average age is in the 40s. The risk of malignancy in cysts with internal drainage is higher than that in primary cysts, and early removal of the retained cyst should be performed as quickly as possible. Although the prognosis of biliary cancer is usually dismal, aggressive procedures are recently gaining better results than that by conventional methods. The prevention of cancer is the procedure of choice by early excision. Removal of the whole extrahepatic bile duct is necessary, even in case of malunion with no biliary dilatation. Cancer rarely arises in the intrahepatic duct after excisional surgery, due to long standing biliary stricture. Wide anastomosis with ductoplasty should be essential. Cancer also occurs in the remnant duct. Excision of the distal duct in the pancreas is also necessary.