Basal cell and squamous cell carcinomas are the most common skin cancers. These are slow-growing cancers that often occur in old people and that are easily cured if they are removed before they spread. The cancers appear on sun-exposed skin, like the nose or cheeks. The risk of these cancers arises in direct proportion to the amount of time people spend in the sun, unlike the much rarer melanomas (cancers of pigmented tissue such as moles and one of the most serious forms with respect to fatal outcome). Cancers of the skin include cancers of the sebaceous glands.
A genetic flaw which impairs the body's immune system could put some people at risk of basal cell and squamous or skin cancers (two of the mildest forms). Basal cell and squamous cancer cells tend to carry a mutated form of a cancer gene, p53, and the mutation is one caused by ultraviolet (UV) light.