BRAF V600E Mutation Across Multiple Tumor Types: Correlation Between DNA-based Sequencing and Mutation-specific Immunohistochemistry.

The B-Raf proto-oncogene (BRAF) encodes a cytoplasmic serine/threonine kinase with a key role in regulating the mitogen-activated protein kinase signal transduction pathway. An activating missense mutation in codon 600 of exon 15 (V600E) of BRAF gene has been identified in multiple neoplasms including melanoma, colorectal carcinoma, papillary thyroid carcinoma, hairy cell leukemia, and Langerhans cell histiocytosis. Patients with BRAF V600E-mutated melanoma respond to FDA-approved BRAF inhibitors. In addition, subsets of other BRAF V600E-mutated tumors may also benefit from BRAF inhibitor therapy. Currently, clinical laboratories typically use molecular-based methods for mutation analysis. However, recently a BRAF V600E mutation-specific antibody has become available as a cost-effective alternative method to DNA-based molecular testing. We analyzed multiple tumor types including melanoma, colorectal carcinoma, papillary thyroid cancer, hairy cell leukemia, and Langerhans cell histiocytosis using both DNA-based sequencing and the BRAF V600E mutation-specific antibody. Our results show a high degree of concordance between the 2 methods. However, the high concordance seems to be limited only to the V600E mutation since variant V600 mutations are missed by V600E mutation-specific immunohistochemistry.