Importantly, our classification of other CNS tumours such as gliomas relies heavily on molecular status whereas meningiomas have been almost entirely classified using histopathology until recently in 2021, when the World Health Organization (WHO) grading incorporated homozygous loss of CDKN2A/B (cyclin-dependent kinase inhibitor 2A/B) and TERT (telomerase reverse transcriptase) promoter (TERTp) mutation as criteria for grade 3 meningiomas. This evidence concerns the gene CDKN2A and meningioma.