As per WHO CNS classification 2016, grade II diffuse astrocytomas and grade III anaplastic astrocytomas are now divided into Isocitrate Dehydrogenase (IDH)-mutant, IDH-wildtype and not otherwise specified(NOS) categories. About 10 % of cases of low grade glioma that arises in young and having IDH1 mutation progress to secondary glioblastoma(GBM). So IDH sequencing is highly recommended. The study aims to show the presence of IDH1 mutation in low grade gliomas (grade II & III) and GBM and classify them as per new WHO CNS Classification 2016.Two out of five cases (40%) of anaplastic astrocytoma, nine out of fifteen cases(60%) were diffuse astrocytoma, three out of three(100%) of secondary GBM(sGBM) and none out of twenty-four of twenty-fourof primary GBM(pGBM) were IDH1 positive. Classifying grade II & III gliomas into IDH mutant and wild type categories reduces NOS Catagories. Immunohistochemistry (IHC) is a simple and valuable diagnostic tool in assessing the IDH1 mutational status.
