Usefulness of peroral cholangioscopy in the differential diagnosis of IgG4-related sclerosing cholangitis and extrahepatic cholangiocarcinoma: a single-center retrospective study.

Characteristic POCS findings of the stricture sites in IgG4-SC were smooth mucosal surface, dilated vessels without caliber alteration and disruption, and lack of easily bleeding. These POCS findings are extremely useful for distinguishing between IgG4-SC and ECC.