How do people get skin cancer?

The most common causes of skin cancer are:
Exposure to ultraviolet radiation from the sun between 10:00 a.m. and 3:00 p.m. and exposure at high altitudes.
Damage to the DNA of melanocytes from exposure to the sun and its UV light radiation is the single most important factor in the cause of melanoma.
Tanning salons also expose your body to UV radiation and increase your risk of developing melanoma.
The depletion of the ozone layer may be significantly affecting the incidence of melanoma. It is estimated that there is a 1% increase in melanoma with each percentage decrease in the ozone layer.
Family history of melanoma.
Atypical moles.
An impaired immune system, especially if you have had an organ transplant, leukemia, or lymphoma. Source(s): I am a nurse for over 20 yrs

it could run in there family,tanning beds,sun
excess sun exposure is the main reason.
Too much tanning - not enough sunscreen.
Usually from years of sun exposure, but there's a familial component, the risk increases with certain drugs and medical conditions, skin type...
tannimg beds and sun burn.