Neurological tumours are common
neoplasms of both adults and children. Recent studies have begun to delineate the genetic abnormalities that underlie such tumours, and have implicated two classes of genes, oncogenes and tumour suppressor genes. Most investigations have focused on those
astrocytomas that affect the cerebral hemispheres of adults, since these are the most common and malignant brain tumours. The high-grade
astrocytomas that affect adults, such as
glioblastoma multiforme, often have amplification of the
epidermal growth factor receptor (EGFR) oncogene and loss of a variety of chromosomal loci that probably harbour tumour suppressor genes. Of the various tumour suppressor gene loci, the p53 gene on chromosome 17p has been studied most closely and has been shown to be mutated in both low- and high-grade
astrocytomas. These genetic alterations may provide a means for subdividing
astrocytomas into diagnostic categories. For instance, p53 gene mutations occur more commonly in
glioblastomas from young adults and women, while EGFR gene amplification is more common in
glioblastomas from older adults and men. For the other primary CNS tumours, genetic studies remain in their infancy. The
neurocutaneous syndromes, such as
neurofibromatosis types 1 and 2, have provided unique insights into neurological
oncogenesis. The NF1 gene on chromosomes 17q and its product,
neurofibromin, may be important in the formation of
neurofibrosarcomas, while the NF2 gene on chromosome 22q and its product,
merlin, are probably involved in the formation of
schwannomas and other nervous system tumours. The further characterization of these and other neurological tumour genes will undoubtedly illuminate many other areas in neurooncology.