Additionally, the presence of a CCNE1 deletion occurred exclusively in cluster 2 (8/10) chordomas and low-risk-group (6/10) chordomas, whereas all RB1 and CDKN2A/2B deletions occurred in cluster 1 and RB1 (5/6) deletions and CDKN2A/2B (2/3) deletions patients who were in the high-risk group. This evidence concerns the gene RB1 and chordoma.