Secondary prevention

Melanocytic nevi are largely genetically determined and cannot be prevented.[19]

The use of sunscreen may be associated with fewer nevi in white children with freckled skin, but more studies with homogeneous methodology and long-term follow-up are needed to clarify the effects of sun exposure on the development of nevi across all races.[15] One systematic review of 15 studies including 20,743 children reported that only 3 of the included studies found that sunscreen protected children from the development of melanocytic nevi.[95] Furthermore, one prospective randomised controlled trial found that sun protection advice at well-child care visits did not reduce tanning, freckling, or number of nevi in children over a 3-year period.[96] The development of melanoma is likely to be a multi-factorial process, and genetics, as well as environmental factors, are likely to play a role in its development. Ultraviolet (UV) exposure is almost certainly a factor in the development of some types of melanoma, particularly lentigo maligna, which is characteristically found on the face of sun-damaged, older, white people.[24][71][97][98]​ However, in other types of melanoma (for example, acral lesions that are on non-sun-exposed skin, and melanomas in darker pigmented races), UV exposure may not play a role.[24][98][99]

Because risk factors for melanoma and other skin cancers related to the sun may be shared by those at high risk for acquiring nevi, it is reasonable to practise safe-sun methods, as sun exposure may be the only modifiable or preventable risk factor. Liberal use of a broad-spectrum sunscreen with UVA and UVB coverage and at least an SPF of 15, if not higher, is recommended to possibly prevent the acquisition of nevi and decrease the risk of sun-related skin cancer.[12][13][18][26][27]​ Recommendations are to apply the sunscreen half an hour before sun exposure, to re-apply every 2 hours, and re-apply more frequently if sweating, swimming, or towelling off.[27] Sunscreen use is encouraged on a daily basis to prevent incidental daily sun exposure, on cloudy days, and in the winter. Sun-protective clothing with a tight weave is encouraged, as well as avoidance of sun exposure from 10 a.m. to 4 p.m., when the sun's rays are most intense.[27] In concert with these recommendations is the avoidance of tanning beds.[27] Skin self-examinations should be done on a regular basis to familiarise patients with their skin and to monitor for any changing or suspicious lesions.[27]

The US Preventive Services Task Force (USPSTF) recommend that children, adolescents, and young adults aged 10 to 24 years who have fair skin be counselled on skin cancer prevention.[100]​ They report that there is insufficient evidence that counselling adults older than 24 years resulted in more benefits than harms, however, recommendations from major dermatological societies suggest that all patients with fair skin should be counselled about skin cancer prevention. The USPSTF do not recommend visual skin examination by a clinician to screen for skin cancer in adolescents and adults due to insufficient evidence to assess the balance of benefits and harms.[74]​​

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