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Etiology of malignant melanoma

Familial disposition

5-10% of all cases have a familial disposition. To use the definition "melanoma family," at least two first-degree relatives or at least three family members must have developed the tumor. 

People with accumulation of malignant melanoma in the family should be referred to a genetic evaluation. This also applies to people with two relatives with malignant melanoma, where one of them has had two or more melanomas. People with incidence of both pancreatic cancer and malignant melanoma among close relatives (possibly the same person) should also be offered genetic evaluation.

People with increased risk of malignant melanoma are offered follow-up. The aim is early diagnosis and treatment, which are believed to improve the prognosis.

Birth marks

About 1% of all newborns have birth marks, of which most are small. There is an increase in malignancy development in large birth marks. It has not been proven whether there is an increased risk for developing melanoma in small and medium-sized birth marks (4).

Atypical melanoma/dysplastic nevus syndrome

Familial incidence of atypical nevi is categorized as atypical mole syndrome (AMS). The National Institute of Health (NIH) defines AMS as:

  • incidence of melanoma in one or more 1st or 2nd degree family members
  • high number of moles, at least > 50 including atypical moles
  • moles which meet criteria for atypical histology

Atypical moles pose an increased risk for developing melanoma. The greatest risk factor is atypical moles in people from families with one or two family members who have had melanoma. It is unclear whether isolated moles themselves can be considered pre-stages for melanoma, or whether these lesions indicate a skin type that more easily develops atypical moles and melanoma.

Sun rays on the skin can, in addition to many beneficial effects such as vitamin D synthesis, suntan, and wellness, cause DNA damage in multiplying cells. Over time, this damage can lead to cancer.

UVA/UVB radiation

Epidemiological studies provide evidence that sunlight influences the development of melanoma. Studies document that within the same population there is a higher incidence of melanoma within decreasing latitudes.

The incidence of melanoma is higher among people who work indoors and visit southern destinations causing intermittent, strong UV exposure.

Sunscreen has been shown to reduce:

  • DNA damage in the skin after exposure to UV light
  • UV induced immunosupression 
  • the development of moles (The strongest isolated risk factor for developing melanoma.)
  • age-induced skin changes
  • incidence of actinic keratosis and squamous cell carcinoma 

There is also scientific evidence that regular use of sunscreen reduces the risk of developing melanoma . The Norwegian Cancer Society and Norwegian Melanoma Group recommends using sunscreen (at least SPF 15) if physical protection is not possible .

Risk Factors

  • Full agreement has not been reached whether the risk is increased by use of solarium, however, based on known skin damage from UV radiation and conclusions from different studies in the field, the Norwegian Melanoma Group does not recommend use of solariums. They recommend using strong precaution under 18 years of age as UV exposure in childhood is more detrimental. IARC published in 2007 a ​​review article which concludes that the risk of melanoma increases by 75% for people who use solarium before 35 years of age (19). An 18-year age limit has been introduced from 1th of July 2012 in Norway. In addition, all tanning salons must be staffed with competent personnel from 1th of January 2014.
  • A large number of benign moles are a risk factor for developing melanoma. (8)
  • Studies associate the incidence of melanoma with the use of chemicals. (5)

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