Familial meningioma: analysis of expression of neurofibromatosis 2 protein Merlin. Report of two cases.

Meningiomas are primarily benign brain tumors thought to arise through multistep tumorigenesis, involving both the activation of oncogenes and the loss of tumor suppressor genes. The recently isolated neurofibromatosis 2 (NF2) tumor suppressor gene has been found to be mutated in a large proportion of meningiomas. Almost all cases of familial meningioma occur in association with NF2. Familial meningioma in isolation from NF2 (sporadic) is exceedingly rare, with only 14 reports since 1959. The authors report the existence of a family lacking any stigmata of NF2, in which two members had spinal meningiomas. Tumor specimens were subjected to immunocytochemical analysis for the NF2 protein product Merlin, which has been implicated in the tumorigenesis of meningioma. Merlin immunoreactivity was present in both tumor specimens, implying that the NF2 tumor suppressor gene was not deleted in these tumors. This supports the hypothesis that a second tumor suppressor gene locus, other than NF2, acts in the formation of familial sporadic meningioma. The results are discussed in the context of putative oncogenic mechanisms of familial meningiomas.