Redefining resection margins and dissection planes in perihilar cholangiocarcinoma-radical resection is a rare event.

Radical tumor resection (pR0) is prognostic for disease-free and overall survival after resection of perihilar cholangiocarcinoma (pCCA). However, no universal agreement exists on the definition of radical resection and histopathological reporting. The aim of this study was to provide a standardized protocol for histopathological assessment and reporting of the surgical specimen obtained after resection for pCCA. All consecutive patients operated for pCCA with curative intent at the Karolinska University Hospital, Stockholm, Sweden between 2012 and 2021 were included. A standardized protocol for histopathological assessment and reporting of the surgical specimen after liver resection for pCCA is presented. A detailed mapping of the transection margins and dissection planes was performed. The results of applying different existing pR0 definitions were compared. Sixty-eight patients with pCCA were included. Five transection margins and two dissection planes were defined. By defining pR0 as cancer-free margins and planes tolerating distances <1mm, the pR0 rate was 66%. However, when pR0 was set as >1mm from invasive cancer to all resection margins and dissection planes, the pR0 rate fell to 16%. This study supports the use of thorough and standardized pathological handling, assessment and reporting of resection margins and dissection planes of surgical specimens of pCCA.