Ultraviolet-B signature mutations have also been identified in the PTCH gene in BCCs (Gailani et al, 1996; Wolter et al, 1997; Lindstrom et al, 2006; Heitzer et al, 2007), and the mutational inactivation of PTCH, rather than TP53, is likely to be rate limiting for BCC. The gene discussed is TP53; the disease is skin basal cell carcinoma.