The role of immunohistochemistry in the identification of BRAF V600E mutated colorectal cancer

BRAF proto-oncogene activating mutations are found in about 8% of human neoplasms and over 90% of BRAF mu- tated tumours display the V600E mutation. BRAF mutation is detected in about 10% of colorectal cancers (CRCs), more frequently in tumours with microsatellite instability (MSI). BRAF status evaluation is a crucial step in the diagnostic al- gorithm for the identification of hereditary (Lynch syndrome) CRCs. Moreover, BRAF mutation is a strong prognostic and predictive factor especially in patients with metastatic disease, and is considered a fundamental parameter in any proposed molecular classification of CRC. In clinical practice BRAF V600E mutation is commonly detected by DNA-based molecular methods. While having very good sensitivity and specificity, molecular analysis is burdened by high costs and needs for skilled professionals, factors limiting its widespread availability. Immunohistochemistry (IHC) using monoclonal antibody VE1 directed against BRAF V600E mutated protein has been recently proposed as a less expensive and widely employable method, with shorter turn-around time. Several studies proved its accuracy in a variety of tumours, with excel- lent concordance rates between IHC and molecular methods. Aim of our work was to compare direct DNA sequencing with IHC in the detection of BRAF V600E mutation in colorectal carcinomas.