IDH1 and astrocytoma (excluding glioblastoma): To identify molecular abnormalities conspiring with IDH mutation in the pathogenesis of LGGs, we performed whole exome capture, next-generation sequencing on genomic DNA extracted from 4 WHO grade II gliomas—3 astrocytomas and 1 oligoastrocytoma—with known mutations in IDH1. Additionally, all 4 tumors were 1p/19q-intact.