A pancreatic mass and extreme elevation of CA 19-9: a benign masquerade of cholangiocarcinoma.

Carbohydrate antigen 19-9 (CA 19-9) is a specific tumour marker for pancreato-biliary malignancy. Immunoglobulin G4-related disease (IgG4-RD) is an immune-mediated condition in which IgG4 deposits infiltrate various organs, including the biliary tract manifesting IgG4 sclerosing cholangitis and pseudotumours. An 83-year-old woman presented with severe obstructive jaundice, weight loss and an extreme elevation of CA 19-9 level of 3295 kU/L. Magnetic resonance cholangiopancreatography (MRCP) revealed a pancreatic mass amputating the biliary tree. Liver function tests revealed a cholestatic pattern and severe hyperbilirubinaemia (289umol/L). IgG4 level was found to be high at 7.97 g/L. After treatment with high-dose corticosteroids, repeat MRCP 2 months later revealed disappearance of the pancreatic mass. There was also normalization of the bilirubin and a dramatic decrease of CA 19-9. This case reports the highest published benign elevation of Ca19.9 level in the setting of IgG4 disease. Differentiation between cholangiocarcinoma and IgG4-RD is important, as the treatment is vastly different.