Prolonged Sun Exposure and Malignant Melanoma
Prolonged UV radiation exposure causes approximately 65-90% of melanomas through DNA damage, and prevention through UV avoidance—particularly during childhood—is the most effective strategy to reduce melanoma mortality. 1
Mechanism of UV-Induced Melanoma
UV radiation causes melanoma through distinct pathophysiologic mechanisms depending on exposure pattern:
Both UVA and UVB radiation contribute to melanoma development, with UVA penetrating deeply into skin causing DNA damage, oxidative stress, immune suppression, and premature aging, while UVB directly damages DNA and causes sunburns. 1, 2
Intermittent intense UV exposures carry higher melanoma risk than chronic cumulative exposure, even when total UV dose is equivalent—this distinguishes melanoma from squamous cell carcinoma. 1, 3
Severe blistering sunburns, particularly in childhood and adolescence, strongly increase melanoma risk by promoting DNA damage during critical developmental periods and increasing the number of moles (a key melanoma risk factor). 1, 4
The biologic mechanism centers on UV-induced DNA damage that dysregulates melanocyte growth control, leading to malignant transformation. 1, 2
Critical Timing: Childhood Exposure
More than half of lifetime UV exposure occurs during childhood and adolescence, making this the most critical prevention window. 1
Children and adolescents have more opportunities for sun exposure than adults, and UV exposure during these periods plays a disproportionate role in future melanoma development. 1
Sun exposure in childhood increases melanoma risk by increasing the number of moles, which are themselves independent melanoma risk factors. 1
History of more than one sunburn in childhood or adolescence is strongly associated with melanoma development in adulthood. 1, 4
Epidemiology and Burden
The melanoma epidemic reflects changing UV exposure patterns:
Melanoma incidence has more than doubled since 1973 (from 5.7 to 14.3 cases per 100,000), while most other cancers are decreasing. 1
An estimated 98,000 new melanoma cases will be diagnosed in the US in 2023, with 8,000 deaths. 1
Five-year survival ranges from 99.5% for localized disease to 31.9% for distant-stage disease, emphasizing the critical importance of early detection. 1
White individuals have approximately 20 times higher melanoma incidence than Black individuals, reflecting the protective effect of melanin pigmentation. 1, 5
High-Risk Populations
Identify patients requiring intensive prevention counseling:
Fair skin (Fitzpatrick types I-II) that burns easily, red or blond hair, light-colored eyes, and freckling are the strongest constitutional risk factors. 1, 4, 5, 6
Large numbers of moles, atypical/dysplastic nevi, and personal or family history of melanoma substantially increase risk. 1, 4, 6
Indoor tanning bed use is an important modifiable risk factor, particularly in adolescents, as these devices emit both UVA and UVB radiation. 1
Older age and male sex are associated with increased melanoma risk and mortality. 1
Prevention Strategies
UV avoidance is the cornerstone of melanoma prevention and is largely effective when implemented early:
The USPSTF recommends counseling all young adults, adolescents, children, and parents of young children (ages 6 months to 24 years) with fair skin about minimizing UV exposure (B recommendation). 1
Protective measures include sun-protective clothing, broad-spectrum sunscreen protecting against both UVA and UVB, avoiding peak sun hours (10 AM-4 PM), and avoiding indoor tanning beds entirely. 1
For adults older than 24 years with fair skin, selectively offer counseling based on individual risk factors (C recommendation). 1
The Community Preventive Services Task Force recommends structured prevention interventions in schools, outdoor occupational settings, and communities. 1
Screening Considerations
The USPSTF concludes there is insufficient evidence to recommend for or against routine visual skin examination screening in asymptomatic adults (I statement). 1
However, clinicians should maintain vigilance:
Visual skin examination using the ABCDE criteria (Asymmetry, Border irregularity, Color variation, Diameter >6mm, Evolution over time) or the "ugly duckling" sign (lesions that look different from other moles) aids detection. 1
Sensitivity of visual examination ranges from 40-70% with specificity of 86-98% for melanoma detection. 1
Most melanomas are detected either by patients discovering lesions or by clinicians finding them incidentally, not through systematic screening. 1
Any suspicious pigmented lesion requires biopsy with deep scoop shave, saucerization, punch biopsy, or full-thickness excision to ensure accurate Breslow depth measurement. 6
Treatment Overview
Early-stage melanoma is treated with wide local excision with appropriate margins, which is curative for thin lesions (Breslow depth <0.8 mm). 1, 6
Lesions with Breslow depth >0.8 mm may require sentinel lymph node biopsy, gene mutation analysis, and consideration of adjuvant immunotherapy or targeted therapy. 1, 6
Systemic immunotherapies have dramatically improved prognosis for advanced melanoma, with 5-year survival for stage III disease now 74.8% (compared to 62.6% before immunotherapy availability). 6
Clinical Pitfalls
Do not assume that darker-skinned individuals are immune to melanoma—acral lentiginous melanoma (occurring on palms, soles, or under nails) is the most common melanoma type in Black populations and is not related to sun exposure. 1
Recognize that intermittent intense exposures (beach vacations, tanning beds) pose higher melanoma risk than chronic occupational exposure, which primarily increases squamous cell carcinoma risk. 1, 3
Avoid dismissing childhood sunburns as inconsequential—they represent the highest-risk exposure pattern for future melanoma development. 1, 4