Toward a molecular classification of the gliomas: histopathology, molecular genetics, and gene expression profiling

As many as 100,000 new cases of brain tumor are diagnosed each year in the United States. About half of these are primary gliomas and the remaining ha lf are metastatic tumors and non-glial primary tumors. Currently, gliomas a re classified based on phenotypic characteristics. Recent progress in the e lucidation of genetic alterations found in gliomas have raised the exciting possibility of using genetic and molecular analyses to resolve some of the problematic issues currently associated with the histological approach to glioma classification. Recently, immunohistochemical studies using novel pr oliferation markers have significantly advanced the assessment of tumor gro wth potential and the grading criteria of some tumor subtypes. Preliminary studies using cDNA array technologies suggest that the profiling of gene ex pression patterns may provide a novel and meaningful approach to glioma cla ssification and subclassification. Furthermore, cDNA array technologies may also be used to identify candidate genes involved in glioma tumor developm ent, invasion, and progression. This review summarizes current glioma class ification schemes that are based on histopathological characteristics and d iscusses the potential for using cDNA array technology in the molecular cla ssification of gliomas.