A 51-year-old woman presented with a 3-week history of painless obstructive jaundice on a background of diet-controlled type 2 diabetes mellitus and significant weight loss. There was no history of inflammatory bowel disease. Physical examination revealed cachexia and jaundice. Relevant blood tests showed bilirubin, 56 μmol/L; alkaline phosphatase 1069 IU/L; gamma-glutyamyltransferase, 1114 IU/L; raised carbohydrate antigen 19-9 level, 213 kU/L; and normal carcinoembryonic antigen level, 2.1 ng/mL.Ultrasound showed common hepatic duct wall thickening and second-order duct involvement bilaterally (Fig. 1). Computed tomography (CT) scan revealed intrahepatic duct dilatation and a hilar stricture suspicious for a Klatskin-type cholangiocarcinoma (CCa) (Fig. 2). Magnetic resonance cholangiopancreatography reported an irregular, enhancing soft-tissue mass at the porta hepatitis ( Fig. 1). Staging laparoscopy revealed no evidence of hepatic or peritoneal metastasis. Percutaneous transhepatic cholangiogram and temporary biliary stent decompression was performed and subsequently right portal vein embolization to stimulate preoperative left lobe hypertrophy.An open extended right hepatectomy including segment 4B was undertaken. Operative findings included no demonstrable left lobe involvement or vascular invasion on intraoperative ultrasound. Extended lymphadenectomy was complicated by a pancreatic capsule injury, repaired intraoperatively.Histopathology did not confirm carcinoma of the stricture but features of immunoglobulin G4 (IgG4) autoimmune-related disease, with plasma cells in the wall of the gallbladder (>50 per high power field), with the majority being IgG4 positive. Sections of the left hepatic duct showed marked dilatation and chronic inflammation throughout the wall consisting of plasma cells and lymphocytes with scanty neutrophils and eosinophils (Fig. 3). Immunoglobulin levels were unremarkable (IgG level 11.4 g/L and IgG4 level 11.5 g/L).One week post-operatively, the patient developed abdominal distension with leucocytosis. CT scan revealed a pancreatic fistula with acute fluid collection and a reactive pancolitis, which required endo-Fig 1. Ultrasound reported (a) the presence of a mass (44 mm × 32 mm) at the porta hepatitis and (b) thickening of the biliary duct wall. Magnetic resonance imaging cholangio-pancreatogram reported (c) dilatation of the right and left hepatic ducts to the level of the porta hepatitis with (d) evidence of a soft-tissue mass in keeping with a hilar cholangiocarcinoma.Fig. 2. Initial computed tomography scan reveals (a) collapse of the common bile duct and (b) dilatation of the left intrahepatic duct.Fig. 3. Macroscopical analysis of the resected surgical specimen revealed (a) a white firm area at the hilum of the liver (arrows), involving the biliary ductal system and adherent to the wall of the gallbladder and extending into the intrahepatic biliary tributaries. (b) Immunohistochemical staining revealed large numbers of IgG4-positive plasma cells (40× original magnification)...