No one knows why some individuals get skin cancers and others do not. The exact cause(s) is unknown but we do know of certain risk factors which can predispose one to developing skin cancers. The risk factors for all skins cancers include:
Sun exposure: Continuous and prolonged exposure to the sun's rays (UV light) is the major risk for all skin cancers. People who work outdoors, like farmers, gardeners, are the most prone to skin cancers. Tanning booths are also a high risk for skin cancers.
Caucasians: Most skin cancers occur in Caucasians or fair skin people. One should beware that melanoma can occur in black people.
Occupation: Individuals who work with coal tar, arsenic or in the radiation industry are also prone to developing skin cancers
Medications: Immunosuppressive drugs administered to patients who have undergone organ transplantation can cause skin cancers. Any suspicious skin lesions in these patients is routinely biopsied
Family history: Skin cancers are slightly more common in individuals with a family history of the disorder.
Atypical moles: There are certain moles which are very large or grow hair and these moles are at high risk for degenerating into melanomas
Chronic wounds: None healing ulcers or chronic burns can degenerate into skin cancers (marjolin's ulcer). Any wound which has been present for years, should always be biopsied to ensure that there is no underlying cancer
Although one can avoid many of these risk factors, one can still develop skin cancer. Some individuals are just more sensitive to the development of skin cancer.
Avoiding sunlight is a key to the prevention of skin cancer. While this does not guarantee that skin cancer will not occur, at least your chances will be very much reduced