Skin cancer is the abnormal growth of skin cells. It may first appear as a new mole, a change in a growth or mole, a sore that does not heal, or an irritation of the skin.

Exposure to the sun is the most common cause of skin cancer. Problems with the body's defense system (impaired immune system) and a family history of skin cancer also increase a person's risk.

There are 3 major types of skin cancer:

• Basal cell skin cancer is the most common form. It is a slow-growing cancer that seldom spreads to other parts of the body.
• Squamous cell skin cancer is less common than the basal cell form. It also rarely spreads, especially if it is found and treated early. However, squamous cell skin cancer is more likely to spread than basal cell carcinoma.
• Melanoma grows and spreads rapidly and can invade other organs, such as the liver, lungs, or brain. Melanoma usually begins in a mole.

Skin cancer is treated by removing the cancerous area with either surgery (excision) or freezing (cryotherapy). Chemotherapy and radiation therapy may be needed to treat an aggressive form of skin cancer or one that has spread to other parts of the body.