The importance of UV-irradiation in the development of cutaneous squamous cell carcinoma (SCC) is well established, and studies of premalignant actinic keratosis (AK) lesions and experimental skin cancers in mice suggest that a key event in the development of skin SCC is the acquisition by epidermal keratinocytes of UV-induced Tp53 gene mutations, characteristically (C to T or CC to TT) transitions at dipyrimidine sites [6], [7], [8]. This evidence concerns the gene TP53 and skin cancer.