Desmoplastic non-infantile astrocytoma/ganglioglioma: rare low-grade tumor with frequent BRAF V600E mutation.

Desmoplastic infantile astrocytoma/ganglioglioma (DIA/DIG) are rare primary glioneuronal tumors that comprise 0.5% to 1.0% of all intracranial tumors. While BRAF mutation is found in up to 50% of pediatric gangliogliomas, data for DIA/DIGs is limited. This study was carried out to evaluate the frequency of BRAF V600E mutation in DIA/DIG. All cases of DIA/DIGs diagnosed over 7 years (2010-2016) were reviewed retrospectively. The clinical, radiological and histopathological characteristics of these patients were evaluated along with immunohistochemical analysis for glial and neuronal markers. We evaluated presence of BRAF V600E mutation by Sanger sequencing and immunohistochemistry using monoclonal antibody against clone VE1. Eight cases of desmoplastic infantile astrocytoma/ganglioglioma (6 DIGs and 2 DIAs) were evaluated. Four cases were of infantile type (age 10 months-2 years) and 4 cases of non-infantile type (age 10-14 years). BRAF VE1 immunohistochemistry (IHC) was positive in four cases (two DIG and two DIA). All these four cases also showed heterozygous BRAF V600E mutation (T replaced by A at nucleotide position 1799). Sequencing didn't detect BRAF mutation in any additional case. All four cases harboring this mutation were non-infantile (10-14 years). Cases with infantile presentation didn't carry this mutation. None of the cases showed recurrence on follow-up. Thus BRAF V600E mutation is common in desmoplastic non-infantile astrocytoma/ganglioglioma, but does not affect the prognosis. Identification of BRAF status opens the possibility of targeted therapies for the subset of cases that clinically progress post-resection.