CDKN2A and chordoma: As one of the most prevalent genetic alterations in chordoma, homo- (11.25–30% in chordoma) or heterozygous loss of chromosome 9p21 (about 70% in chordoma) with loci of cyclin-dependent kinase inhibitor 2A/2B (CDKN2A/2B), has been described in several cohorts (Bai et al. 2021; Le et al. 2011; Tarpey et al. 2017).