The amount of skin cancer has increased dramatically during the past two decades, mainly because of cumulative exposure to the ultraviolet rays of the sun. If current trends continue, the National Cancer Institute warns, from 40 percent to 50 percent of all Americans who live to age 65 will develop at least one skin cancer. Skin cancer falls into two broad areas: non-melanoma skin cancer (basal-cell cancer and squamous-cell cancer), and melanoma.

The most common skin cancers are basal-cell and squamous-cell carcinomas. These are non-melanoma skin cancers that are slow growing, easily treated and rarely lead to death. At least 1 million cases of basal-cell and squamous-cell skin cancers occur each year in the United States, more than twice the number diagnosed 20 years ago.

When neglected, non-melanoma skin cancers can grow large enough to become disfiguring and can spread. Squamous-cell cancers cause an estimated 2,200 deaths in the United States yearly.

Malignant melanoma is less common, but more dangerous. Melanoma accounts for less than 5 percent of all skin-cancer cases in the United States but 75 percent of skin-cancer deaths. Approximately 60,000 new cases are diagnosed each year, and the disease claims about 8,100 lives. The incidence of melanoma has increased dramatically over the past decade, but survival rates also have improved because more cases are being diagnosed early.

Like most cancers, the risk of melanoma increases with age. People of all ages, however, have some risk of melanoma.

Although skin cancer can occur in people of all races, those with darker skin typically have a lower risk because their skin contains more of the pigment melanin, which protects against skin cancer. Melanoma occurs 10 times more often among whites than African Americans, and two to four times more frequently among whites than Hispanics. The incidence of skin cancer has increased dramatically among whites during the past decade, but has remained stable among African Americans.