Background: Simultaneous double cancers of the biliary tract are rare. Most of them are thought to be associated with pancreaticobiliary maljunction (PBM); however, the characteristics of tumours without PBM are still unclear.
Methods: Histology, immunoreactivity with carcinoembryonic antigen, carbohydrate antigen 19-9 and p53 and mutations in the K-ras gene were examined in tumours resected from cases of simultaneous double cancers of the biliary tract.
Results: Four cases of simultaneous double cancers of the biliary tract were identified among 108 patients with biliary tract cancer (3.7%). None of the four cases associated with PBM, and the results of histological, immunohistochemical and genetic examinations differed between the bile duct and gall bladder cancers in each case.
Conclusion: Even when they do not associate with PBM, double cancers in the biliary tract are more likely to be the result of multicentric development.