Clonal analysis of human meningiomas and schwannomas.

Meningiomas and schwannomas are two of the most common tumors of the human nervous system. To determine whether these tumors arise from a single cell or from multiple cells, we used molecular genetic techniques to study X chromosome inactivation in meningiomas and schwannomas isolated from females including one who had neurofibromatosis type 2. The tumors were also screened for loss of heterozygosity at several loci on chromosome 22 using polymorphic DNA markers. Among nine meningiomas, at least three of which showed loss of alleles on chromosome 22 and five of which retained heterozygosity for the chromosome 22 alleles examined, all nine tumors were monoclonal. Among eight schwannomas, at least seven of which retained heterozygosity for chromosome 22 loci, seven were monoclonal. We conclude that human meningiomas and schwannomas arise from a single cell.