What are the risk factors and causes of melanoma?

Causes and Risk Factors of Melanoma

Ultraviolet (UV) radiation exposure is the primary preventable cause of melanoma, accounting for approximately 65-90% of all cases, with both UVA and UVB radiation causing DNA damage that plays a central role in melanoma development. 1

Primary Environmental Causes

UV Radiation Exposure Patterns

Intermittent intense UV exposure carries higher melanoma risk than chronic cumulative exposure, even when total UV dose is equivalent. 1

• Severe, blistering sunburns are strongly associated with increased melanoma risk, particularly when occurring during childhood and adolescence 1
• Beach vacations, previous sunburn history, and recreational sun exposure show significant risk increases 2
• More than half of lifetime UV exposure occurs before age 20, making childhood a critical susceptible window 1, 3
• History of >1 sunburns in childhood or adolescence is strongly related to melanoma development 1, 4

Artificial UV Sources

Sunlamps and tanning beds are carcinogenic, with first exposure before age 30 increasing melanoma risk by 75%. 1, 5

• The National Institute of Environmental Health Sciences concluded in 2000 that artificial UV radiation is carcinogenic 1
• Some tanning beds emit UV radiation similar to or exceeding noontime summer sun 1
• Indoor tanning is causally associated with melanoma according to the International Agency for Research on Cancer 5

Host Risk Factors

Skin Phenotype

Fair-skinned individuals who sunburn readily and tan poorly face approximately 20-fold higher melanoma incidence compared to darker skin types. 6

• Red or blond hair, fair skin that freckles or burns easily confer highest risk 1
• Melanoma incidence among whites is 20 times higher than among blacks and 4 times higher than among Hispanics 1
• Fair skin that freckles easily requires annual full-body skin examinations due to significantly elevated melanoma risk 6

Melanocytic Nevi (Moles)

Large numbers and unusual types of moles are the most measurable predictors of melanoma. 1

• Moles begin appearing during childhood and adolescence and are associated with sun exposure 1
• Sun exposure in childhood increases melanoma risk by increasing the number of moles 1
• A changing mole, particularly in adults, is often indicative of melanoma development 1

Genetic Factors

Family history of melanoma increases risk up to 8-fold, though only 10% of melanoma patients have positive family history. 1

• Risk increases with >1 first-degree relatives (mother, father, brother, sister) with melanoma 1
• High numbers of nevi and freckles, red hair, blue eyes, and inability to tan are primary genetic determinants in adolescents 3
• Genetic referral is indicated for individuals with hereditary syndromes including Carney complex, Peutz-Jeghers syndrome, Constitutional Mismatch Repair Deficiency, and Neurofibromatosis Type 1 6

Environmental Modifiers of UV Exposure

Geographic and temporal factors significantly modify UV radiation intensity and melanoma risk. 1

• Latitude closer to the equator increases UV exposure 1, 7
• Higher altitude increases UV radiation 1, 7
• Light cloud coverage allows 80% of UV rays to penetrate 1
• Reflective surfaces (pavement, water, snow, sand) increase exposure 1, 7
• UV-B radiation peaks between 10 AM and 4 PM, especially 11 AM to 1 PM 1
• Spring and summer months carry higher UV exposure 1
• Ozone depletion potentially increases surface UV radiation 1

Age-Related Risk

Melanoma incidence increases exponentially with age, yet approximately half of all melanomas occur in persons <50 years. 1

• Melanoma is one of the most common cancers in persons <30 years 1
• Elderly men (>65 years) account for 22% of newly diagnosed melanomas annually 1
• Older persons have diminished capacity to repair UV-induced DNA damage 1

Critical Clinical Pitfalls

Acral lentiginous melanoma occurs on non-sun-exposed sites (palms, soles, nail beds) and is the most common melanoma type in Black populations—do not overlook these areas. 6

• Delaying dermatology referral for any changing, irregular, or symptomatic pigmented lesions can be critical 6
• Providing false reassurance about melanoma risk in fair-skinned patients with multiple pigmented lesions should be avoided 6
• Chronic occupational sun exposure may actually be associated with reduced melanoma risk, contrasting with intermittent exposure patterns 2