Skin cancer is a type of cancer that begins in cells of the skin. Skin cancer is the most common type of cancer in humans. Ultraviolet light exposure from the sun or tanning beds is the greatest risk factor for developing skin cancers.
The most common type of skin cancer is a basal cell cancer. These begin in the so-called basal cells of the upper layer of skin, the epidermis. They tend to form in sun-exposed areas of skin. Basal cell cancers do not usually spread to other parts of the body (metastasize), and they can typically be cured if they can be surgically removed. Squamous cell cancers are cancers of the cells that form the flattened cells of the epidermis. Like basal cell cancers, they usually occur in areas exposed to sunlight. Squamous cell cancers also can typically be cured if they can be surgically removed. Basal cell cancers often appear as a waxy or pearly bump on the skin. Squamous and basal cell cancers can appear as flat lesions, reddened nodules, or scaling or scar-like areas.
Melanomas are less common but are a more serious form of skin cancer. Melanoma can develop anywhere on the body. Melanomas often appear as new moles or moles that appear to have changed in appearance. Melanomas can spread to other parts of the body and can be fatal if not treated early.