Melanoma causes and risk factors

This page was reviewed under our medical and editorial policy by

Maurie Markman, MD, President, Medicine & Science

This page was updated on July 14, 2022.

Each year, more than 100,000 Americans are diagnosed with melanoma. No one knows if or when the disease will develop, but understanding the causes and risk factors for melanoma may help patients take preventive measures to reduce the likelihood of developing the disease. Reducing controllable factors may help lower the risk of getting melanoma or other forms of skin cancer. For factors that can’t be controlled, regular skin examinations may help spot a developing melanoma in early stages, when it is more treatable.

What causes melanoma?

Melanoma develops when skin cells called melanocytes mutate and begin to grow out of control. Unlike more common skin cancers, melanoma may be found on parts of the body not normally exposed to the sun, such as the groin or armpits.

While the exact cause of melanoma may not be known, several factors may increase the risk of developing the disease. The primary risk factor for melanoma is exposure to ultraviolet (UV) light, typically from the sun and tanning beds, with the risk growing with the amount of exposure. Early exposure, particularly for people who had frequent sunburns as a child, also increases melanoma risk.

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Melanoma risk factors

Sun or tanning bed UV exposure

People who work outdoors during the day or who choose to spend much of their leisure time outdoors and are exposed to UV light are at an increased risk. People who choose to use tanning beds increase their risk of skin cancer. Frequent sunburns, especially when they occurred during childhood, increase the risk of developing melanoma.

Other melanoma causes and risk factors

Age: As with many cancers, melanoma risks increase as people age. Nearly half of all new melanoma cases are diagnosed in patients between the ages of 55 and 74. But melanoma can affect people of all ages. In fact, melanoma is the most common type of cancer among women ages 25 to 29.

Immune suppression: Conditions that weaken the immune system, such as viruses, diseases or immune suppression therapy associated with organ transplantation, may increase risks for all skin cancers, including melanoma.

Skin tone: Caucasians have a greater risk of developing skin cancer, including melanoma, than non-whites. The risk is also higher for individuals with blond or red hair, blue or green eyes, or skin that burns or freckles easily.

Moles: Most moles are harmless and never develop into cancer, but having a large number of moles may increase the risk of developing melanoma. The presence of dysplastic nevi (moles that may resemble melanoma) may also increase risk, by 10 percent. Although most dysplastic nevi will not develop into melanoma, a small percentage may, and individuals with these types of moles should see a dermatologist regularly for thorough skin exams.

Is melanoma genetic?

Genetic factors may contribute to the risk of developing melanoma:

Family and/or personal history: Individuals with one or more parents or siblings with melanoma may be at increased risk. Individuals who have previously been diagnosed with melanoma are also at increased risk for developing the disease again.

Inherited conditions: Conditions such as xeroderma pigmentosum, an inherited disease that affects the skin’s ability to repair UV damage, are at increased risk for developing melanoma, and may develop them at an earlier age.

Learn more about diagnosing melanoma

Next topic: What are the symptoms of melanoma?

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