Clinical relevance of BRAF status in glial and glioneuronal tumors: A systematic review

Alterations in the BRAF gene have been reported to play a key role in the tumorigenesis of various tumors. Recent studies have shown the existence of BRAF alterations in ganglioglioma (GG), pilocytic astrocytoma (PA), pleomorphic xanthoastrocytomas (PXA), and epithelioid glioblastoma (eGBM). The focus of this review was the association between the clinical characteristics and BRAF status in these glial and glioneuronal tumors. The BRAF abnormalities, KIAA1549-BRAF fusion and BRAF mutation, were detected in approximately 50% of the analyzed tumors regardless of the tumor location, and there were site-specific BRAF abnormalities that became more remarkable on analysis by each tumor subtype. The median age of patients with KIAA1549-BRAF fusion was much lesser than that of those with BRAF mutations. Histological analysis indicates that the existence of KIAA1549-BRAF fusion is related to pilocytic morphology. The review of imaging features indicated that cyst formation is associated with the existence of KIAA1549-BRAF fusion in PA and GG and the lack of BRAF mutation in GG. Hemorrhage was significantly present in cases of GG with KIAA1549-BRAF fusion, but no relevance was shown in cases with BRAF mutations. No significant relevance was detected between the presence of calcification and BRAF alterations. Our clinical and genetic review of BRAF-related tumors indicated that the KIAA1549-BRAF fusion was strongly associated with PA, but not with other glial and glioneuronal tumors.