CDKN2A and meningioma: Furthermore, the subgroup analysis of combining old WHO grading with CDKN2A/B status confirmed the present WHO grading regarding the importance of homozygous CDKN2A/B deletions because those with a previously diagnosed WHO grade 2 meningioma despite a homozygous CDKN2A/B deletion had a shorter time to meningioma progression compared with those with a WHO grade 3 meningioma combined with a CDKN2A/B wild-type status.