Premalignant manifestations of photoaging: Actinic keratoses and atypical nevi

Long-term exposure to ultraviolet (UY) radiation produces the visible signs of photoaging and, more significantly, skin cancer. The three common types of skin cancer are basal cell carcinoma, squamous cell carcinoma (SCC), and melanoma. Current estimates indicate that about 1.3 million new cases of skin cancer occur each year in the United States alone. Of this total, about 80% are basal cell carcinoma, 15% are SCC, and 5% are melanoma. Basal cell carcinoma arises de novo on normal-appearing sun-damaged skin. Therefore, treatment is not currently possible until a visible tumor is detected. In contrast, SCC has a readily identifiable precursor, the actinic keratosis. Similarly, atypical, or dysplastic, nevi may be a marker for individuals predisposed to melanoma. The identification of precursors and risk markers allow the clinician the opportunity for early intervention and preventative measures. This chapter reviews the epidemiology, pathogenesis, diagnosis, and management of the most common precursor lesions of skin cancer-actinic keratoses and atypical nevi.