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Oncogenesis after cyst excision for choledochal cyst and suitable surgical procedures for this operation are discussed. The clinical data of 23 patients with cancer of the biliary tree after excision of choledochal cyst reported in the English-language and Japanese literature were reviewed, and data for 1353 Japanese patients with choledochal cyst and/or pancreaticobiliary malunion were analyzed. In the 23 patients reported in the literature, age at cyst excision ranged from 1 to 55 years (average, 23.0 +/- 13.7 years), and cancers were detected at age 18-60 years (average, 32.1 +/- 12.2 years), with intervals between cyst excision and cancer detection of 1-19 years (average, 9.0 +/- 5.5 years). Sites of cancer development were: intrahepatic, six; anastomotic, eight; hepatic side residual cyst, three; and the intrapancreatic duct, six. In the Japanese patients with choledochal cyst and/or pancreaticobiliary malunion, the incidence of cancer associated with primary choledochal cyst and/or pancreaticobiliary malunion was 16.2% (219/1353). The incidence of cancer development after cyst excision in this population, of whom 1291/1353 underwent surgery, was assumed to be 0. 7%. Nearly half of the 23 patients in the literature had undergone inadequate cyst excision. Oncogenesis of cancers after cyst excision is possibly different from that of choledochal cysts.

Congenital biliary cysts occur not only in the choledochus but also everywhere in the biliary tree, and are frequently accompanied by pancreatobiliary malunion. Alonso-Lej and colleagues first classified choledochal cysts into three types, in 1959. Due to the recognition of intrahepatic involvement, we refined their classification into six types, in 1977, and this has become the reference. However, this classification does not include the concept of pancreatobiliary malunion and has caused some confusion, especially in regard to types Ic and IVA. Type Ic, showing fusiform dilatation, has a pancreatobiliary malunion and often extends continuously to the intrahepatic duct. Type IVA, with intrahepatic involvement, shows primary ductal stricture, especially around the hepatic hilum and umbilicus. The incidence of the stricture is considerably greater than was previously assumed, and upstream intrahepatic ducts often join the dilated duct, with distinct caliber change. Intrahepatic dilatation may develop primarily, due to the stricture, combined with weakness of the duct wall. This stricture can be corrected by portal dissection in the liver to obtain a large anastomosis. In patients with intrahepatic involvement, we should carefully find the stricture by suitable cholangiograms, or by intraoperative cholangioscopy. Detecting the ductal stricture is obviously important, rather than classifying the cyst as type Ic or IVA.

The incidence of carcinoma arising in the wall of the congenital bile duct cysts is much higher than previously assumed. The authors report 4 such cases of primary and secondary carcinomas and review their clinical features through the similar 59 cases in the literature. Of the 63 cases, the average age was much younger, at least several decades, compared with cases of extra-hepatic carcinoma without bile duct cysts. The female-male ratio was 2.5:1. Racial preponderance was also observed, namely, the majority were Japanese. Additionally, many patients previously received various internal drainage procedures, especially choledochocystoduodenostomy. As the treatment, primary excision of the extrahepatic bile duct cyst seems to give the best results because it can avoid ascending cholangitis and prevent development of carcinoma. However, carcinoma still can arise in the intrahepatic bile duct cyst, which cannot be removed at the present time.

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