MG3 and MG4 meningiomas were enriched for prognostically unfavorable alterations including TERTp mutation and homozygous loss of CDKN2A/B, in addition to novel somatic mutations in KDM6A, CHD2, and PTEN, and these tumors had a significantly higher degree of chromosomal instability. This evidence concerns the gene PTEN and meningioma.