CDKN2A and melanoma: However, not all melanoma families with p16 mutations do have abnormally large naevi (Hayward, 2003; Kefford et al, 2004); likewise members bearing the same p16 mutation within a single family can vary as to whether they have large naevi (Gruis et al, 1995), which suggests variation between humans in the contribution of p16 compared to other genetic (or environmental) components in determining mole size distribution.