Ultraviolet carcinogenesis in nonmelanoma skin cancer. Part I: incidence rates in relation to geographic locations and in migrant populations.

Over the past two decades a worldwide increase in the incidence of skin cancer to near epidemic proportions has led to increased morbidity and appreciating cost. Well known risk factors include UV radiation, x or gamma irradiation, chemical carcinogens, genetic aberrations, and immunosuppression. This article reviews and analyzes the evidence for UV radiations role in the pathogenesis of nonmelanoma skin cancer (NMSC). Observations on the incidence of NMSC among migrants to temperate regions show an increase in both basal cell carcinoma and squamous cell carcinoma. There is also an increase in NMSC in areas with lower latitudes. Irradiation of human skin grafted to animals and animal models that develop NMSC lend further support to the role of UV radiation in the pathogenesis of NMSC. In the forthcoming Part II of this review, epidemiologic evidence will be presented attesting to the relationship between UV radiation and NMSC.