In IDH-mutant astrocytomas, chromosomal instability is an established poor prognostic factor.39 Its prognostic value in AO remains to be fully established, yet it has been associated with more frequent contrast-enhancement, larger tumor volume, and a poorer prognosis.23,38 Chromosome 9p loss and CDKN2A deletion have been shown to be important poor prognostic factors in AO.21 Herein, there was a trend toward more frequent 9p loss in STS compared to CS, but this trend was not statistically significant, possibly because of the small sample size. Here, CDKN2A is linked to neoplasm.