Genetic analysis suggests the presence of four clinically relevant groups of histologically defined anaplastic oligodendrogliomas. Genetic analysis suggests the presence of four clinically relevant groups of histologically defined anaplastic oligodendrogliomas. Median values are given for age, duration of response, and survival from diagnosis (dx). *, group 2 patients have 1p loss but either do not have 19q loss or have other genetics alterations such as TP53 mutation, PTEN mutation, 10q loss, EGFR amplification, or CDKN2A deletion. **, group 4 patients often had PTEN mutation, 10q loss, EGFR amplification, CDKN2A deletion, and ring enhancement. Yasushi Ino et al. Clin Cancer Res 2001;7:839-845 ©2001 by American Association for Cancer Research