Analysis of the BRAFV600E Mutation in Central Nervous System Tumors

BRAF^V600E mutations are involved in the development of melanoma, colon cancer, and papillary thyroid carcinoma. These mutations are also found in primary brain tumors at low to moderate frequencies. In this study, we investigated a series of brain tumors to determine the prevalence and associated clinicopathologic features of BRAF^V600E mutations. By direct sequencing, we analyzed 223 brain tumors, including 51 gangliogliomas (GGs), 45 pilocytic astrocytomas (PAs), 12 pleomorphic xanthoastrocytomas (PXAs), 35 glioblastomas (GBs), 28 anaplastic astrocytomas (AAs), 44 oligodendroglial tumors (ODGs), 3 anaplastic oligoastrocytomas, and 5 diffuse astrocytomas. Thirty-six cases (16.1%) exhibited the BRAF^V600E mutation, including 66.7% of PXAs, 23.5% of GGs, 15.6% of PAs, and 9.7% of the malignant gliomas; the latter included 14.3% of AAs, 8.6% of GBs, and 4.5% of ODGs. Copy number aberration at the 7q34 (BRAF) locus was found in 73.1% of PAs and 50% of PXAs. 9p Homozygous deletion was found in 66.7% of PXAs, but it was not correlated with the BRAF^V600E mutation. Patients' age, sex, histologic grade, and progression-free survival were also not correlated with the BRAF^V600E mutation. The BRAF^V600E mutation in brain tumors did not have prognostic value but is certainly a diagnostic marker and therapeutic target, not only for pediatric low-grade gliomas but also for malignant gliomas, even though the rate of mutation was not high. These results should be verified in a larger study with more cases and a longer follow-up period to overcome the limitation of small sample size.