NF2 and meningioma: Monosomy of chromosome 22 is observed in 40–70% of meningioma cases, supporting a role of NF2. Although deletions of chromosome 22 affect prevalently the NF2 gene [5,6], there are a variety of extents in chromosome 22 loss that do not affect NF2. This suggests the presence of adjacent genes on chromosome 22q that play a role in meningioma tumorigenesis.