Immunohistochemistry is highly sensitive and specific for the detection of NRASQ61R mutation in melanoma

Mod Pathol. 2015 Apr;28(4):487-97. doi: 10.1038/modpathol.2014.137. Epub 2014 Oct 24.


Testing for NRAS is now integral part in the assessment of metastatic melanoma patients because there is evidence that NRAS-mutated patients may be sensitive to MEK inhibitors, and RAS mutation is a common mechanism of acquired resistance during treatment with BRAF inhibitors. This study evaluated the sensitivity and specificity of immunohistochemical analysis using an N-Ras (Q61R) antibody to detect the presence of the NRASQ61R mutation in melanoma patients. A total of 98 primary cutaneous melanomas that have undergone examination of NRAS mutation were retrieved from a multicentric database. Formalin-fixed and paraffin-embedded melanoma tissues were analyzed for BRAF and NRAS mutations by independent, blinded observers using both conventional DNA molecular techniques and immunohistochemistry with the novel anti-human N-Ras (Q61R) monoclonal antibody (clone SP174). The antibody showed a sensitivity of 100% (14/14) and a specificity of 100% (83/83) for detecting the presence of an NRASQ61R mutation. Of the NRAS-mutated cases, none of the non-Q61R cases stained positive with the antibody (0/7). There were three cases with discordant NRAS mutational results. Additional molecular analysis confirmed the immunohistochemically obtained NRAS result in all cases, suggesting that a multiple analytical approach can be required to reach the correct sample classification. The reported immunohistochemical method is an accurate, rapid, and cost-effective method for detecting NRASQ61R mutation in melanoma patients, and represents a valuable supplement to traditional mutation testing. If validated in further studies, genetic testing would only be required for immunohistochemistry-negative patients to detect non-Q61R mutations.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Female
  • GTP Phosphohydrolases / genetics
  • GTP Phosphohydrolases / metabolism*
  • Humans
  • Immunohistochemistry*
  • Male
  • Melanoma / genetics
  • Melanoma / metabolism*
  • Melanoma / pathology
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Middle Aged
  • Mutation*
  • Sensitivity and Specificity
  • Skin Neoplasms / genetics
  • Skin Neoplasms / metabolism*
  • Skin Neoplasms / pathology
  • Young Adult


  • Membrane Proteins
  • GTP Phosphohydrolases
  • NRAS protein, human