Melanoma Cause & Risk

Today, it is not clear why melanoma occurs. Some risk factors have been identified. A risk factor increases the risk that cancer occurs, but is neither necessary nor sufficient to cause cancer. A risk factor is not a cause in itself. 

Some people with these risks factors will never develop melanoma and some people without any of these risk factors will develop melanoma. 

The main risk factors of melanoma are: 

Skin type: people with fair skin have a higher risk of developing melanoma than people with darker skin. The highest risk concerns people with red hair and freckles. Melanoma is actually very rare in black or Asian people.

Naevi: a naevus is the medical term for a mole. The majority of moles will never turn into cancer, but the presence of many (more than 100) moles or unusual moles indicates an increased individual risk of developing melanoma. 

  • Having multiple common naevi increases the risk of developing melanoma. The risk increases with the number of naevi and is particularly high when the number of naevi is above 100. 
  • Having 3 or more atypical naevi increases the risk of developing melanoma. An atypical naevus is defined as a naevus presenting at least 3 of the ‘ABCD’ characteristics: Asymmetry in its shape, Border irregularity or a border which is ill‐defined, Colour varying from one area to another and Dynamic evolution over time regarding its shape, colour or size. 
  • Congenital naevi are moles that are present from birth. Large (>5cm) congenital moles are at risk of turning into melanoma. Persons with large congenital naevus should be followed up on a regular basis. 

Sun exposure: natural exposure to ultraviolet (UV) radiation emitted by the sun is an important risk factor for melanoma. The following factors increase the risk at every stage of life but are worse when exposure occurs in early childhood. 

  • Intermittent sun exposure, usually for recreational purposes, increases the risk of developing melanoma. 
  • Sunburn increases the risk of developing melanoma, especially sunburns, during childhood. 
  • Using sunscreen may reduce the risk of developing melanoma. It should be associated with other simple rules such as avoiding being in the sun between 11 am and 3 pm, and covering up with clothes, a broad hat and sunglasses when exposed to the sun. 

Sun bed use: exposure to artificial UV light to get a tan increases the risk of developing melanoma especially when sun beds are used before the age of 30. 

History of melanoma:

  • Having had melanoma increases the risk of having another melanoma at a different location 
  • Having a first‐degree relative (parents, siblings and children) who had melanoma increases the risk of having melanoma. Some inherited gene mutations are known, such as the CDKN2A mutation, but gene mutations are found in less than 50% of the melanoma families. 

Age: the risk of melanoma increases with age although melanoma is less associated with aging than other types of cancer and it can occur in people who are under the age 30. 

Gender: in North‐America, Oceania and Israel men have a higher risk of developing melanoma while in Europe the risk is slightly higher in women. 

Immune suppression: people with lowered immunity are at a higher risk of developing melanoma. Immunity can be lowered because of a disease such as AIDS or because of drugs given after an organ transplant. 

Xeroderma pigmentosum: it is a rare and inherited disease in which the ability to repair damage caused by ultraviolet light is impaired. For these people, the risk of developing all types of skin cancers including melanoma is extremely high. 

Other factors, such as exposure to pesticides or having Parkinson’s disease are suspected to be associated with an increased risk of melanoma, but evidence of and reasons for these associations remain unclear.


Source: Melanoma: a guide for patients ‐ Information based on ESMO Clinical Practice Guidelines ‐ v.2011.2