According to the Consortium to Inform Molecular and Practical Approaches to CNS Tumour Taxonomy Not Official WHO (cIMPACT-NOW) consortium, a definitive diagnosis of WHO grade 4 astrocytoma requires IDH mutation, ATRX loss, Tumour Protein-p53 (TP53) mutation, and absence of 1p/19q code deletion [3]. The gene discussed is IDH1; the disease is astrocytoma (excluding glioblastoma).