Skin cancer is by far the most common cancer. More than 600,000 cases are diagnosed each year. Skin cancers involve abnormal cell changes in the epidermis or outermost layer of the skin. Most of these cancers involve the highly curable basal cell and squamous cell carcinomas, which are nonmelanoma cancers.
Malignant melanoma, the most serious skin cancer, is diagnosed in about 32,000 people annually, and its incidence is increasing by 4 percent per year. The increasing incidence of all types of skin cancer is believed to arise from a widespread change in lifestyle with greater exposure of successive generations to sunlight, specifically ultraviolet radiation. Limiting the skin's exposure to this radiation could prevent many cases of skin cancer.
The main cause of skin cancer is excessive exposure to sunlight, which contains ultraviolet rays. Tanning beds, sunlamps and X-rays also generate ultraviolet rays that can cause skin cancer. Squamous cell and basal cell cancers have been associated with chronic sun exposure, most frequently with fair-skinned people who work outside. Melanoma is linked with infrequent but excessive sunbathing that causes scorching sunburn.