BRAF alterations in pediatric low grade gliomas and mixed neuronal-glial tumors.

Low grade astrocytomas are the most common brain tumor in children. Recent studies have identified alterations in the BRAF serine/threonine kinase gene that result in mitogen activated protein kinase pathway activation. Herewith, we investigated the genetic changes of BRAF in pediatric low grade gliomas and their relation to pathological findings and Ki-67 proliferation index. The results showed gene fusions between KIAA1549 and BRAF in 66.7 % of tumors. The majority involved the KIAA1549-BRAF exon 16-exon 9 variant. Fusion junction between KIAA1549 exon 15 and BRAF exon 9 was found in five tumors, in which the myxoid component was the predominant. This has not been previously reported. No significant correlation was found between specific KIAA1549 and BRAF fusion junctions and Ki-67 index. All of the samples included in this study were tested for the presence of the BRAF(V600E) mutation, and no positive sample was found.