Other common paediatric CNS tumours are ependymomas and pilocytic astrocytomas.
Glioblastomas are the most malignant brain tumours in adults.
There is extensive evidence for the involvement of both oncogenes and tumour suppressor genes in the oncogenesis and progression of primary CNS tumours. In order to understand the nature of molecular abnormalities during oncogenesis and progression, we have investigated abnormalities of some tumour suppressor genes and oncogenes in such tumours Loss of one wild type TP53 allele combined with mutation of the retained allele has been shown in adult astrocytic gliomas. Involvement of the TP53 gene in the development of paediatric tumours had not been investigated. We examined 33 cases of paediatric CNS tumours for loss of alleles on chromosome 17 and for mutations of the TP53 gene. We found that 5 PNET cases had loss of chromosome 17p together with isochromosome l7q.