The Great Mimicker Victoria Gómez and Jaime Aranda Michel Department of Gastroenterology and Hepatology, Mayo Clinic, Jacksonville, Florida Question: A 65-year-old woman was evaluated for recurrent painless jaun- dice. Prior investigations at an outside institution included an endoscopic retrograde cholangiopan- creatography that showed a stricture in the distal common bile duct with a negative cytology for malig- nant cells. She underwent laparotomy, during which a pancreatic head mass was found and biopsies re- vealed no malignancy. A palliative cholecystojejuno- stomy with gastroenteros- tomy was performed. Post- operatively, the jaundice improved but she remained with epigastric pain, persistent nausea, anorexia, and a 20-pound weight loss. Two weeks later, she developed recurrent jaundice and a second endoscopic retrograde cholangiopancreatography demonstrated a hilar stricture. A presumptive diagnosis of multicentric cholangiocarcinoma was made and she was referred to hospice care. She then sought another opinion regarding her condition at our institution. Enhanced computed tomography (CT) of the abdomen with focus on the pancreas (Figure A) showed mild peripancreatic inflammation and glandular enlargement (arrow points to endoscopically placed biliary endoprosthesis). Percutaneous transhepatic cholangiography (Figure B) showed multiple smooth stenoses in the intrahepatic ducts (arrows). Serum immunoglobulin (Ig) G4 levels were normal. She underwent an endoscopic ultrasonography, which showed no evidence of a pancreatic head mass. However, the entire pancreas was diffusely inhomogeneous and abnormal. The parenchyma presented alternating hypoechogenic and hyperechogenic areas with strands and lobulations. The outer border of the gland was lobular and the main pancreatic duct was normal. Biopsies of the pancreas showed changes consistent with chronic pancreatitis with loss of the acinar parenchyma and residual islets and ducts seen with fibrosis and infiltration composed of mononuclear cells. Immunostain for CD138 was performed and very high numbers of plasma cells were observed infiltrating the tissue. Immunostain for IgG4 demonstrated approximately 10 –15 positive cells per high-power field. What is the diagnosis? Look on page 1694 for the answer and see the GASTROENTEROLOGY web site (www.gastrojournal.org) for more information on submitting your favorite image to Clinical Challenges and Images in GI. Conflicts of interest: The authors disclose no conflicts. © 2012 by the AGA Institute 0016-5085/$36.00 http://dx.doi.org/10.1053/j.gastro.2012.07.111 Clinical Challenges and Images in GI, continued 1441