Table 3.
NF2 gene mutation frequencies in meningiomas of different histological subtypes.
| Histological subtype | Total no. | NF2 gene mutation frequency1 | Chr. 22 deletions affecting the NF2 gene | Biallelic inactivation of the NF2 gene |
| Meningothelial | 33 | 6/33 (18%) | 13/33 (39%) | 6/33 (18%) |
| Transitional | 31 | 13/31 (42%) | 20/31(65%) | 12/31(39%) |
| Fibroblastic | 21 | 11/21 (52%) | 18/21 (86%)4 | 11/21 (52%)5 |
| Anaplastic | 8 | 5/8 (61%)2 | 5/8 (61%) | 4/8(50%) |
| Psammomatous | 4 | 2/4 (50%)3 | 3/4 (75%) | 2/4 (50%) |
| Unclassified | 3 | 1/3 (33%) | 1/3 (33%) | 1/3 (33%) |
| Overall | 100 | 39 | 60 | 36 |
1 The methylation status of NF2 gene promoter in tumor M104 is not included.
2 The two micro deletions (1 bp and 7 bp) detected in M169 within exon 12 are considered as one.
3 Two point mutations were detected in M22, only one is used for calculations.
4 Fifteen of the 18 fibroblastic meningiomas that display deletions on chromosome 22 are monosomy cases. The three remaining tumors (M64, M32, and M114) all disclose a minimum of 18 Mb deletion of 22q.
5 Case M64 (biallelic deletion affecting the NF2 gene) is not included in this calculation