Given these results, which suggest that primary atypical meningiomas were overwhelmingly associated with loss of NF2, we divided our cohort into two large subgroups: those with NF2 mutations, and those that were NF2 wild type (including TRAF7/PI3K//KLF4, Hedgehog and POLR2A mutant tumours as well as mutation unknown samples). This evidence concerns the gene PIK3CA and meningioma.