Gliomas are the most common primary brain tumor, and are histopathologically classified
according to their cell type and the degree of malignancy. However, sometimes diagnosis can be controversial,
and tumors of the same entity possibly have a wide range of survival. Genetic analysis of
these tumors is considered to have great importance in terms that it can provide clinically relevant
classification of the tumors and compensate for the limitation of the histological classification. Previous
studies using comparative genomic hybridization (CGH) demonstrated that copy number aberrations
(CNAs) were frequently recognized in these tumors, and revealed that a gain on chromosomal arm 7q
was the most common CNA in diffuse astrocytomas, whereas a small population of the tumor showed
losses on 1p/19q which characterizes oligodendrogliomas with good responsiveness to chemotherapeutic
regime using procarbazine, nitrosourea and vincristine. High grade (malignant) gliomas
(i.e. anaplastic astrocytomas, anaplastic oligodendrogliomas and glioblastomas) have been reported to
have a gain on 7p and losses on 9p and 10q. In case of ependymomas, frequent chromosomal aberrations
in intracranial tumors were a gain on 1q and losses on 6q, and, on the other hand, a gain on
chromosome 7 was recognized almost exclusively in spinal cord tumors. These data suggest that intracranial
and spinal cord ependymomas are different genetic diseases and comprise different subgroups
within one histological entity. In conclusion, genetic analysis of gliomas may help to classify these
tumors and provide leads concerning their initiation and progression. The relationship of these aberrations
to patient outcome needs to be addressed. |