Chromosomal composition of a series of 22 human low-grade gliomas.

G-banded chromosomal analysis was performed on direct and/or in vitro cultures of 22 low-grade gliomas, including nine grade I-II astrocytomas, nine oligodendrogliomas, one mixed tumor oligodendroglioma-astrocytoma, and three ependymomas. Normal diploid stem lines were present in most astrocytomas and oligodendrogliomas, whereas, all three ependymomas displayed polyploid modal numbers. However, secondary cell lines showed the presence of clonal recurrent numerical abnormalities, mainly polysomy 7, monosomy 10 and 22, and loss of the Y chromosome. Clonal structural rearrangements were present with a low incidence; they mainly involved chromosomes #1 and #7. These patterns of chromosome involvement seem to correlate with the scarce previous cytogenetic banding data available from low-grade gliomas. They are also similar to the chromosome alterations found in high-grade gliomas.