We do not yet know exactly what causes melanoma skin cancer. But we do know that certain risk factors are linked to this disease. A risk factor is anything that affects your chance of getting a disease. Different cancers have different risk factors. Some risk factors, like smoking, can be controlled. Others, like a person's age or family history, can't be changed.
But risk factors don't tell us everything. Having a risk factor, or even several risk factors, does not mean that you will get the disease. And many people who get the disease may not have any known risk factors. Even if a person with melanoma has a risk factor, it is often very hard to know how much that risk factor may have contributed to the cancer.
Risk factors for melanoma skin cancer
UV (ultraviolet) light
Too much exposure to UV radiation is thought to be a major risk factor for most melanomas. The main source of UV light is the sun. Tanning lamps and beds are also sources of UV light. People with high levels of exposure to UV light are at greater risk for all types of skin cancer.
The amount of UV exposure depends on the strength of the light, how long the skin was exposed, and whether the skin was covered with clothing or sunscreen. Many studies have linked melanoma in the trunk and legs to frequent sunburns (especially in childhood).
To find out more about how to protect yourself and your family, see the section called "Can melanoma be prevented?"
Moles
A mole (the medical name is nevus) is a benign (not cancer) skin tumor. Certain types of moles increase a person's chance of getting melanoma. The chance of any single mole turning into cancer is very low. But a person who has many moles is more likely to develop melanoma. These people should have very thorough skin exams by a skin doctor (dermatologist). Many doctors suggest that they should also check their own skin every month. Good sun protection is always important.
Fair skin, freckles, and light hair
The risk of melanoma is more than 10 times higher for whites than for African Americans. Whites with red or blond hair, blue or green eyes, or fair skin that freckles or burns easily are at increased risk.
Family history of melanoma
Around 10% of people with melanoma have a close relative (mother, father, brother, sister, child) who has had the disease. This could be because the family tends to spend more time in the sun, or because the family members have fair skin, or both. Less often, it is because of a gene change (mutation) that runs in the family.
People with a strong family history of melanoma should do these things:
- Have regular skin exams by a skin doctor (dermatologist)
- Learn to look at their own skin and know what it should look like
- Be very careful about sun exposure and avoid tanning beds
Having had melanoma in the past
A person who has already had melanoma has a higher risk of getting another one.
Weak immune system
People who have been treated with medicines that suppress the immune system, such as transplant patients, have an increased risk of melanoma.
Age
Melanoma is more likely to happen in older people. But it is a cancer that is also found in younger people. In fact, it is one of the most common cancers in people under 30.
Gender
In the United States, men have a higher rate of melanoma than women.
Xeroderma pigmentosum (XP)
This is a rare, inherited condition. People with XP are less able to repair damage caused by sunlight and are at greater risk of melanoma and other skin cancers at a young age.
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