NF2 and meningioma: Merlin protein expression was statistically significantly different (P < .05) between groups of different mitotic activity in meningioma (Fig. 1A), as defined by MIB-1 (Ki-67) labeling index (Mitotic index ≥ 4 mitoses/10 HPF and Mitotic index ≥ 20 mitoses/10 HPF) according to the WHO 2016 grading criteria for meningioma.2 We also performed differential expression analysis of Merlin on the basis of the meningioma grade, which classically define aggressive meningiomas.