[Skin carcinogenesis]

Two main distinct subtypes of epithelial skin cancers can be distinguished, both arising from keratinocytes, most frequently at sun-exposed body sites. Basal cell carcinomas (BCC) grow slowly, nearly never metastases, whereas squamous carcinomas (SCC) are locally more invasive tumors, which have a greater metastatic potential. Skin carcinogenesis is a multiple step process, in which UV light play a major role. Numerous genetic lesions occur, either inactivating tumor suppressor genes (which normally repress cell growth), or activating oncogenes (which promote cellular multiplication). The most important tumor suppressor gene involved in both skin neoplasms is p53, which is inactivated in 40-50% of cases, by specific UV induced mutations. Yet, some differences exist between these two subtypes, which could explain their difference in invasiveness.