As discussed below, while the vast majority of IDH-wildtype gliomas in adults do not have ATRX mutations, evidence of ATRX loss, either by IHC or by sequencing panels that assess this gene should prompt consideration of pediatric-type diffuse gliomas, including H3G34-mutant tumors, and other entities including ‘high grade astrocytoma with piloid features’ (HGAP) [7]. The gene discussed is IDH1; the disease is high grade astrocytic tumor.