This reveals that most of the substitutions enriched in MCC samples have indeed occurred at cytidines (bins ending at 1,200 bp, P = 0.0036; 1,400 bp, P < 0.0001; 1,600 bp, P = 0.0207; 1,800 bp, P = 0.0363; 2,000 bp, P = 0.0007; 2,400 bp, P = 0.0494) and that the cytidines account for most of the mutations between RB and helicase domains (bins ending at 1,200–2,000 bps). Here, RB1 is linked to Merkel cell skin cancer.