Cytogenetic analysis of gemistocytic cells in gliomas

Gemistocytes are glial cells characterized by voluminous, eosinophilic cytoplasm and a peripherally positioned, often flattened nucleus. Gemistocytes, usually present in anoxic-ischemic brains, are regularly encountered in glial neoplasms. The presence of gemistocytes in gliomas has been associated with an unfavorable clinical course, notwithstanding the low proliferative potential of these cells. It is not known whether gemistocytes residing in gliomas are dormant tumor cells, or alternatively, represent interspersed reactive glial cells. Whereas gemistocytic astrocytomas have been subject to various genetic investigations, no genomic analysis comparing individual cells in gliomas has been reported so far. In the present study, 3 astrocytomas, 3 oligodendrogliomas, and 3 mixed oligoastrocytomas, all harboring gemistocytic cells, were genetically analyzed by DNA in situ hybridization to paraffin-embedded, formalin-fixed tissue samples with optimal preservation of cellular morphology. To this end, probes for the centromeric regions of chromosome 7 and 10, known to show copy number aberrations in gliomas, were used. In addition, probes for centromeric regions of chromosomes 1 and 17 were used for the ploidy status of the tumors. The spot counts for the various chromosomes were statistically compared. Gains of chromosome 7 were found in 1 anaplastic astrocytoma, 1 anaplastic oligodendroglioma, and 1 anaplastic oligoastrocytoma. Loss of chromosome 10 was seen in 2 anaplastic astrocytomas, in 1 anaplastic oligodendroglioma, and in 1 anaplastic oligoastrocytoma. In 3 cases, significant differences in spot distributions between gemistocytes and non-gemistocytes were found, but the other cases showed no difference in spot distribution. It is concluded that, although many gemistocytic cells in gliomas may be considered reactive cells, in a subset of tumors, part of the gemistocytic cells should be considered neoplastic.