CDKN2A and melanoma: As RGP melanomas have few mitoses (Mooi and Krausz, 2007) and exhibit localized p16 and/or p21 in vivo (Gray-Schopfer et al., 2006), they may retain some competence to senesce in some areas, but presumably other areas have evaded senescence and are growing, as a non-growing lesion would not be diagnosed as a melanoma.