When cells are healthy, they grow, divide and replace themselves. These cells comprise the body's tissue. This process of cell duplication is how the body grows, maintains health and keeps in good repair. Some of these cells, however, can lose their ability to perform these tasks. The growth and progress of these cells becomes limited, or they may divide themselves too rapidly or grow without organization. Sometimes, the cells produce too much tissue, resulting in the formation of benign or malignant tumors.

Benign tumors are those which do not lead to cancer. When a tumor is benign, it's not life-threatening and it won't extend to the rest of the body. Once these types of tumors are removed via surgery, they usually won't return. Benign tumors are typically more of a nuisance than a threat.

Malignant tumors are those that will lead to cancer. These tumors invade and destroy the neighboring healthy tissues and organs, causing illness in the body. Malignant tumors can spread or "metastasize" to other organs and cause new tumors to grow throughout the body.

Skin cancer comes in two main forms: basal cell carcinoma and Squamous cell carcinoma. A "carcinoma" is a type of cancer that begins in the cells that cover or surround an organ.

More than 90 percent of skin cancers in the United States are basal cell carcinoma. This type of cancer grows slowly and rarely spreads to other areas. It's crucial, however, that all types of skin cancer are found and treated as early as possible to prevent them from invading and destroying nearby tissues.

Squamous cell carcinoma and basal cell carcinoma are usually referred to as nonmelanoma skin cancer. Melanoma is another form of skin cancer which begins in the melanocytes.

Skin cancers presently account for the most common types of cancer in the United States. An estimated 40 to 50 percent of Americans who live to be 65 years and older will develop skin cancer at least once in their lifetime. It's important to note, however, that people of any age and nationality can develop skin cancer. Fair-skinned, freckled people with red or blond hair and blue or light colored eyes are most risk of developing the disease.

The sun's UV (ultraviolet) radiation is the most common cause of skin cancer. The sun creates two types of ultraviolet radiation: UVA and UVB. Tanning booths and sun beds create artificial UV radiation, and will also cause skin cancer.

Skin cancer affects a greater number of people living in certain areas of the world. Those who live under the hot Texan sun are particularly at risk. Skin cancer rates are also higher in Australia and South Africa, where people are exposed to excessive amounts of the sun's UV rays every day. Those living in these, and other areas where UV exposure is high, are more likely to develop skin cancer.