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PHOTOCARCINOGENESIS

UV-Induced Tumor Formation

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:

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      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 …