Biliary tract cancers (BTC) are aggressive gastrointestinal malignancies that are associated with a poor prognosis. The only potentially curative treatment of BTC is a complete resection with negative microscopic margins. Overall, 5-year survival rates of 20–35% have been reported after resection of EHBD cancer.

One of histologic characteristics in BTC is longitudinally spread along the bile duct wall. In recently, a pre-operative diagnosis for the extension of BTC cancer has improved, it is difficult to decide the surgical resection margin pre-operatively. Therefore BTC is difficult to obtain surgical resection with tumour-free margins.
A positive resection margin has been considered an adverse prognostic factor. The question whether R1 resection irrespective of the reasons for failure to achieve R0 resection offers survival benefit need to be answered since R1 resections are not infrequent clinically. The reasons for R1 resections may be various. First, multifocality of bile duct cancer is present in 10% of EHBD cancer. Second, if the patients are not
in good condition to undergo major resection such as PD and liver resection, surgical option may end up with R1 BDR if any of both resection margins is involved. Third, in many cases, surgeons perform surgery for mid to distal bile duct cancer without relieving the jaundice and estimation of remnant liver function preoperatively. In this situation, adding liver resection to BDR or PD in case of involvement of prximal margin
may be dangerous since it often lead to insufficiency of liver which is already damaged by cholestasis.
In many studies, Invasive carinoma at the ductal resection margins appears to have a more adverse effect on survival, whereas residual CIS/HGD does not. Thereofore resection margin should be obtained as invasive carcinoma free margin.