CDKN2A and meningioma: Released in 2021, the 5th edition of the WHO CNS classification is the first to include molecular criteria for the definition of a CNS WHO grade 3 meningioma: presence of a TERTp hotspot mutation or homozygous loss of CDKN2A/B. These molecular alterations are rare in meningiomas, particularly in cases that do not have other worrisome histologic findings.