BRAF V600E-specific immunohistochemistry reveals low mutation rates in biliary tract cancer and restriction to intrahepatic cholangiocarcinoma

Mod Pathol. 2014 Jul;27(7):1028-34. doi: 10.1038/modpathol.2013.206. Epub 2013 Dec 6.

Abstract

BRAF mutations have emerged as an important predictive biomarker for metastasized melanoma. Other types of cancer may also benefit from BRAF mutation-targeted therapies. In biliary tract cancer, reported BRAF mutation rates are highly controversial, ranging from 0 to 33% in adenocarcinoma of the gallbladder and 0 to 22% in cholangiocarcinoma. We here analyzed tissue microarrays of a large cohort of biliary tract cancer (n=377) including 159 intrahepatic cholangiocarcinomas, 149 extrahepatic cholangiocarcinomas, and 69 adenocarcinomas of the gallbladder for BRAF V600E mutation using a highly sensitive immunohistochemical screening approach implementing the BRAF V600E protein-specific antibody VE1. All VE1-positive cases as well as 42 VE1-negative cases were additionally analyzed by Sanger sequencing. In total, only 5 VE1-positive cases were detected (5/377; 1%). BRAF V600E mutation was confirmed by direct sequencing in all cases. All 5 mutated cases were intrahepatic cholangiocarcinomas (5/159; 3%). None of the extrahepatic cholangiocarcinomas and adenocarcinomas of the gallbladder were VE1 positive. Apart from the subtype restriction of BRAF V600E mutation to intrahepatic cholangiocarcinoma and a female predominance (4 female, 1 male), no significant correlation with clinicopathological data and patient outcome was detected. In conclusion, we demonstrate that BRAF V600E mutation is a rare event in biliary tract cancer, accounting for only 1% of all subtypes, and is restricted to intrahepatic cholangiocarcinoma. In addition, we demonstrate that VE1 immunohistochemistry is a feasible approach to routinely screen for BRAF V600E mutation in biliary tract cancer patients, thereby facilitating the detection of rare patients who may benefit from BRAF mutation-targeted therapies.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Bile Duct Neoplasms / genetics
  • Bile Duct Neoplasms / metabolism*
  • Bile Duct Neoplasms / pathology
  • Bile Ducts, Intrahepatic / metabolism*
  • Bile Ducts, Intrahepatic / pathology
  • Cholangiocarcinoma / genetics
  • Cholangiocarcinoma / metabolism*
  • Cholangiocarcinoma / pathology
  • Female
  • Humans
  • Immunohistochemistry
  • Male
  • Middle Aged
  • Mutation
  • Mutation Rate
  • Proto-Oncogene Proteins B-raf / genetics
  • Proto-Oncogene Proteins B-raf / metabolism*
  • Tissue Array Analysis

Substances

  • BRAF protein, human
  • Proto-Oncogene Proteins B-raf