Epidemiology of actinic keratoses and squamous cell carcinoma

Objective: The purpose of this article was to review the frequency; distrib ution, and determinants of actinic keratoses (AKs) and squamous cell carcin oma (SCC). Methods: A review of the literature was done. Results: AKs are extremely common lesions on the sun-exposed skin of Caucas ian persons. The most important risk factors are a combination of genetic p ropensity ("fair skin phenotype") and cumulative sun exposure. Their preval ence increases with advancing age. The epidemiology of SCC is virtually the same, but the lesions occur most often on the head rather than on the uppe r extremities where most AKs are located. AKs are the most important risk F actor identifying those most predisposed to the development of an SCC. Conclusion: AKs are a reliable marker for those people most predisposed to development of an invasive SCC. In addition, AKs are probably an early stag e in a biologic continuum that culminates in SCC. However, there are many m ore AKs than SCCs, and it is difficult to predict exactly which lesions wil l progress to invasive cancer.