Skin cancer is the most common cancer diagnosed in the United States, affecting over 3 million Americans each year. Skin cancer comes in two primary forms, called nonmelanoma and melanoma. The nonmelanoma skin cancers can be further divided into basal cell and squamous cell carcinomas. The type of skin cancer depends on which cells are affected.

[Page 1262]The skin is formed in three layers—the stratum corneum (the skin's external surface), the epidermis (the thin layer between the stratum corneum and the dermis), and the dermis (the deepest layer, which contains blood vessels, sweat glands, hair follicles, and other tissues). Basal cell carcinomas of the skin arise in the cells that divide the epidermis from the dermis. Squamous cell carcinomas of the skin arise in cells within ...