Rare detection of PTENmutations in grade I–II astrocytomas and secondary glioblastomasmay be associated with methylation of the PTEN promoter, whichis often found in low-grade gliomas and reduces PTEN protein productioncompared to the normal level [84].Mutations in the PTEN gene are more common among olderpatients with anaplastic astrocytoma and young patients with glioblastoma[83]. This evidence concerns the gene PTEN and astrocytoma (excluding glioblastoma).