IDH-mutant tumors can be broadly divided into two groups: those with 1p/19q co-deletion, typically displaying an oligodendroglial morphology, and those without 1p/19q co-deletion, primarily comprising lower-grade astrocytomas enriched for mutations in both alpha thalassemia/mental retardation syndrome X-linked protein (ATRX) and tumor protein 53 (TP53). Here, TP53 is linked to astrocytoma (excluding glioblastoma).