Risk factor		Nonmelanoma skin cancer	Melanoma
Age		More common with increasing age	Peak frequency in early adulthood, but age-related incidence rises with increasing age.
Chemicals and exposures		Use of coal-tar products, tobacco and psoralens (e.g., PUVA therapy) increase risk.	Radiation exposure increases risk.
Family history		No influence on risk	Occurrence of melanoma in a first- or second-degree relative confers increased risk. Familial atypical mole–melanoma syndrome (FAMMS) confers even higher risk.
Gender		Substantially more common in males	Slight male predominance
Geographic location		Higher incidence in whites living near the equator because of greater ultraviolet (UV) light exposure per unit time	Higher incidence in whites living near the equator because of greater UV light exposure per unit time
Medical conditions		Chronic osteomyelitis sinus tracts, burn scars, chronic skin ulcers, xeroderma pigmentosum and human papillomavirus infection all increase risk.	Xeroderma pigmentosum, immunosuppression, other malignancies and previous nonmelanoma skin cancer all increase risk.
Nevi		No influence on risk	Nonfamilial dysplastic nevi, a large number of benign pigmented nevi, and giant pigmented congenital nevi confer increased risk. Nondysplastic nevi are markers for risk, not precursor lesions.
Occupation		Higher incidence in outdoor workers	Higher incidence in indoor workers, as well as those with higher education and income.
Previous history of skin cancer		36 to 52 percent chance of a new skin cancer of any kind within five years of index case	Previous melanoma is associated with increased risk.
Race		More common in whites	More common in whites
Skin type/ethnicity		Increased incidence in those with fair complexions; those who burn easily, tan poorly and freckle; those who have red, blonde or light brown hair; and those of Celtic ancestry	Increased incidence in those with fair complexions; those who burn easily, tan poorly and freckle; those who have red, blonde or light brown hair; and those of Celtic ancestry
Sun exposure
	Cumulative	Single greatest risk factor; 80 percent of lifetime sun exposure is obtained before 18 years of age.	Probably does not influence risk
	Episodic	Probably does not influence risk	Intense, intermittent exposure and blistering sunburns in childhood and adolescence are associated with increased risk.