SOX2 and meningioma: Considering all samples, among grade 1 meningioma, 39.3% showed immunostaining for SOX2; among grade 2 meningioma, 72.9% were positive; among grade 3 meningioma, 94.3% were positive on IHC for SOX2 (p < 0.0001, Chi square test; Figure 2A).