title: Albumin expression distinguishes bile duct adenomas from metastatic adenocarcinoma.
abstract: OBJECTIVE
  Bile duct adenomas may be difficult to distinguish from metastatic carcinomas, particularly well-differentiated pancreatic ductal adenocarcinoma. Prior studies have evaluated the utility of various immunohistochemical markers, although these markers are notable for low sensitivity and/or specificity. The aim of this study was to investigate the utility of albumin and BRAFV600E expression in distinguishing between metastatic pancreatic adenocarcinoma and bile duct adenoma.
  
  
  RESULTS
  We studied 26 bile duct adenomas, three bile duct hamartomas, and 158 pancreatic ductal adenocarcinomas. Branched-chain in-situ hybridization (bISH) for albumin was performed; bISH is based on the branched DNA technology, wherein signal amplification is achieved via a series of sequential steps. Additionally, BRAFV600E immunohistochemistry (IHC) was performed on a subset of cases. Twenty-three of 25 (92%) bile duct adenomas were positive for albumin; 18 (72%) showed diffuse staining, and five showed focal staining (20%), including two challenging examples. Two bile duct hamartomas also stained positively. All pancreatic adenocarcinomas were negative for albumin. Seven of 16 (44%) bile duct adenomas and five of 106 (5%) pancreatic ductal adenocarcinomas were positive for BRAFV600E by IHC. The sensitivity and specificity of expression of albumin, as detected by bISH, for distinguishing bile duct adenomas from metastatic pancreatic adenocarcinomas were 92% and 100%, respectively; the sensitivity and specificity of BRAFV600E IHC for distinguishing bile duct adenomas from metastatic pancreatic adenocarcinomas were 43.8% and 95.3%, respectively.
  
  
  CONCLUSIONS
  Diagnostically challenging examples of bile duct adenoma may be distinguished from metastatic pancreatic adenocarcinoma by the use of albumin bISH.
authors: Pathology Service, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA.
authors: Andrea P
authors: AP
authors: Moy
authors: Pathology Service, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA.
authors: Kshitij
authors: K
authors: Arora
authors: Pathology Service, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA.
authors: Vikram
authors: V
authors: Deshpande
mesh_terms: D000230:Adenocarcinoma / Q000175:diagnosis*; D002759:Adenoma, Bile Duct / Q000175:diagnosis*; D000328:Adult; D000368:Aged; D000418:Albumins / Q000032:analysis / Q000096:biosynthesis*; D001650:Bile Duct Neoplasms / Q000175:diagnosis*; D001653:Bile Ducts, Intrahepatic / Q000473:pathology; D014408:Biomarkers, Tumor / Q000032:analysis*; D021441:Carcinoma, Pancreatic Ductal / Q000175:diagnosis; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D017403:In Situ Hybridization; D008297:Male; D008875:Middle Aged; D010190:Pancreatic Neoplasms / Q000175:diagnosis; D048493:Proto-Oncogene Proteins B-raf / Q000096:biosynthesis; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D046888:Tissue Array Analysis
chemical_list: D000418:Albumins; D014408:Biomarkers, Tumor; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf
keywords: BRAF; albumin; bile duct adenoma; in-situ hybridization