A 77-year-old man with jaundice and a pancreatic head tumor was referred to our hospital in August2006.The initial laboratory tests,computed tomography(CT)scan,magnetic resonance imaging(MRI),and endoscopic retrograde cholangiopancreatography suggested IgG4-related cholangitis and autoimmune pancreatitis.Oral prednisolone(PSL)was then administered.This treatment reduced the size of the pancreatic parenchyma,and the lower common bile duct(CBD)returned to its normal size.Thus,the oral PSL was gradually tapered to a maintenance dose.In February 2010,a CT scan and MRI showed segmental wall thickening and stenosis of the middle CBD,the progression of which led to extrahepatic obstructive jaundice.We suspected the emergence of a cholangiocarcinoma rather than the exacerbation of the IgG4-related sclerosing cholangitis because the stricture of the CBD was short and localized.Then,a percutaneous transhepatic biliary drainage was performed.The biopsy specimens obtained via the percutaneous transhepatic tract indicated an abnormal glandular formation,suggesting the presence of a moderate,well-differencated adenocarcinoma.The gross examination,microscopic examination and immunohistochemical analysis of the pancreaticoduodenectomy specimen suggested that a cholangiocarcinoma developed from the IgG4-related sclerosing cholangitis. A 77-year-old man with jaundice and a pancreatic head tumor was referred to our hospital in August 2006. The initial laboratory tests, computed tomography (CT) scan, magnetic resonance imaging (MRI), and endoscopic retrograde cholangiopancreatography suggested IgG4-related cholangitis and autoimmune pancreatitis. Oral prednisolone (PSL) was then administered. This treatment reduced the size of the pancreatic parenchyma, and the lower common bile duct (CBD) returned to its normal size.Thus, the oral PSL was gradually tapered to a maintenance dose .In February 2010, a CT scan and MRI showed segmental wall thickening and stenosis of the middle CBD, the progression of which led to extrahepatic obstructive jaundice. We suspected the emergence of a cholangiocarcinoma rather than the exacerbation of the IgG4-related sclerosing cholangitis because the stricture of the CBD was short and localized. Then, a percutaneous transhepatic biliary drainage was performed. The biopsy specimens were via the percutaneous transection shepatic tract indicates an abnormal glandular formation, suggesting the presence of a moderate, well-differencated adenocarcinoma. gross examination, microscopic examination and immunohistochemical analysis of the pancreaticoduodenectomy specimen that that cholangiocarcinoma developed from the IgG4-related sclerosing cholangitis.