Out of 19 cases of grade 2 astrocytomas, 57.9% of cases showed IDH1 mutation and 21.1% of cases showed ATRX loss. Among grade 3 astrocytomas, 66.7% of cases showed IDH1 mutation, and 33.3% of cases showed loss of ATRX. Here, IDH1 is linked to astrocytoma (excluding glioblastoma).