Clinical neuropathology practice news 2-2012: BRAF V600E testing

Activating mutations of the serine threonine kinase v-RAF murine sarcoma viral oncogene homologue B1 (BRAF), most commonly of the V600E type, are found in a wide range of human neoplasms including primary and secondary brain tumors. Therapeutic BRAF inhibitors have shown clinically meaningful activity, particularly in metastatic BRAF V600E mutated melanoma including patients with brain metastases. Therefore, in current neuropathological practice BRAF testing is of clinical importance in tissue samples of melanoma brain metastases in order to identify cases amenable to therapy with BRAF inhibitors. BRAF mutation testing may also add additional information for differential diagnosis of primary brain tumors in selected situations, e.g., for differentiation of anaplastic pleomorphic xanthoastrocytoma (BRAF V600E mutation in 65%) from glioblastoma (BRAF V600E mutation in < 5%). The BRAF mutation status can be tested with DNA-based methods and immunohistochemistry using a V600E mutation-specific antibody. In summary, at this point BRAF V600E testing is clinically indicated in relatively few cases of the daily clinical neuropathology practice, but has important predictive implications for patients with melanoma brain metastases. Depending on the results of additional clinical studies, determination of BRAF mutation status may become clinically relevant also for primary brain tumors such as glioblastoma in the future.