It is well established that exposure of the skin to UV light is a major risk factor for the development of cutaneous melanoma and non-melanoma skin cancer^[11]. It is a process that, like cancer in general, involves a stepwise accumulation of specific genetic changes in a single cell, with subsequent clonal expansion. Usually, it takes decades until a tumor arises. It is commonly accepted that UV-induced skin cancers (BCC, SCC and melanoma) develop along the photocarcinogenesis chain of events outlined in Figure 85.5. The three major steps are:

	•	DNA damage formation after UV exposure
	•	mutation formation following DNA damage formation
	•	malignant transformation following mutation formation (see below).

There is limited information regarding which wavelengths of the UV spectrum are responsible for these effects. While the carcinogenic properties of short-wavelength UV light (UVC, UVB) have been well established for some time, UVA has long been thought …