NF2 and meningioma: WHO grade 1 and grade 2–3 meningiomas had the following characteristics: NF2 alteration and/or 22q loss (grade 1, 32.6%; grade 2–3, 100%), bone invasion (grade 1, 9.3%; grade 2–3, 75%), irregular shape (grade 1, 20.9%; grade 2–3, 75%), MIB-1 LI > 4 (grade 1, 20.9%; grade 2–3, 50%), and GTR (grade 1, 62.8%; grade 2–3, 50%; Table 1).