CDKN2A and meningioma: When split by WHO grade, the majority of WHO grade 3 meningiomas with CDKN2A homodel had minimal p16 immunoreactivity (19/22, 87% with “0” or “ + 1” scoring), however as did a large proportion of grade 2 meningiomas both with (3/6, 50% with “0” or “+1” scoring) and without CDKN2A homodel (10/18, 56% with “0” or “+1” scoring) (Fig. 5l).