With regard to target genes, the CDKN2A tumour suppressor gene located on 9p21 is found to be homozygously deleted in about 25% of anaplastic oligodendrogliomas (Cairncross et al, 1998; Bigner et al, 1999; Watanabe et al, 2001a) and the PTEN gene maps to 10q23 is mutated in 8% of anaplastic oligodendrogliomas (Sasaki et al, 2001). Here, PTEN is linked to anaplastic oligodendroglioma.