SPEN and anaplastic oligoastrocytoma: The most frequently mutated genes in the group of five patients with anaplastic oligoastrocytomas were TSC1 (75%), SPEN (50%), IDH (25%), ALK (25%), ARID1A (25%), CIC (25%), MAP3K1 (25%), MLL2 (25%), NF1 (25%), and POLE (25%); See Supplementary Materials S1.