Risk factors for melanoma and keratinocytic cancers

Created 2017.

Identification of high-risk individuals

High-risk individuals have characteristics that justify regular skin checks due to:

• Male sex and age > 50 years
• Previous skin cancer
• Many moles, especially if some are large or otherwise atypical
• Signs of significant sun damage
• Strong family history of skin cancer
• Immunosuppressive drugs
• Genetic syndrome.

Risk factors for melanoma

More than 95% of melanomas relate to sun exposure, specifically exposure to ultraviolet radiation. The relationship is complex. For these melanomas, risk factors are well established. Risk profiling specifically identifies:

• Older, sun-damaged men with slowly-growing atypical lentigines.
• Younger adults with many moles and a history of sunburn.

Rare types of melanoma are equal in incidence in all races and skin types, for example, acrolentiginous, melanoma, mucosal melanoma, melanoma in childhood, noncutaneous melanoma (e.g. ocular) etc.  

Absolute risk factors for melanoma

The risk for an individual is uncertain. There are various online tools to determine this but most are based on non-New Zealand data.

Risk factors for keratinocytic cancers

Risk factors for basal cell carcinoma (BCC) are similar to melanoma, except a lack of association with number of melanocytic naevi. Family history of BCC is possibly more important than for melanoma. Data is lacking. 

Actinic keratosis and squamous cell carcinoma (SCC) are primarily caused by cumulative sun damage rather than being associated with intermittent sunburn.  Outdoor work and recreation and white skin that burns easily in the sun are relatively more important compared to melanoma and basal cell carcinoma.

There are some syndromes that increase risk of SCC / BCC.

• Basal cell naevus syndrome
• Eruptive keratoacanthomas

Immunosuppressive drugs markedly increase the risk of all skin cancers, but especially actinic keratoses and squamous cell carcinomas. Organ transplant recipients should be under regular surveillance.