PDGFB and meningioma: In the group of PGDStv-a;RCAS-PDGF-B;AdCre;Nf2flox2/flox;Cdkn2ab−/− mice, we observed 33% (5/15) of grade I meningiomas, 47% (7/15) of grade II meningiomas and 20% (3/15) of grade III meningiomas.