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Causes
By Mayo Clinic staffMelanoma is the most serious and deadly type of skin cancer. Although melanomas make up the smallest percentage of all skin cancers, they cause the greatest number of deaths. That's because they're more likely to spread to different parts of your body. And the incidence of melanoma is on the rise.
Melanoma occurs when something goes awry in the melanin-producing cells (melanocytes) that give color to your skin. Normally, skin cells develop in a controlled and orderly way — healthy new cells push older cells toward your skin's surface, where they die and eventually are sloughed off. This process is controlled by DNA — the genetic material that contains the instructions for every chemical and biological process in your body. But when DNA is damaged, new cells may begin to grow out of control and can eventually form a mass of cancerous cells.
Just what damages DNA in skin cells and how this leads to melanoma is a matter of intense study. Cancer is a complex disease that often results from a combination of factors, including environmental and genetic factors, rather than from a single cause. Still, excessive exposure to ultraviolet (UV) radiation is a leading factor in the development of melanoma, whether the radiation is from the sun or from tanning lamps and beds.
UV radiation and melanoma
UV radiation is produced by the sun. UV light is divided into three wavelength bands — ultraviolet A (UVA), ultraviolet B (UVB) and ultraviolet C (UVC). Only UVA and UVB rays reach the earth — UVC radiation is completely absorbed by atmospheric ozone, a naturally occurring substance that filters UV radiation. Commercial tanning lamps and tanning beds also produce UV radiation.
UVB light causes harmful changes in skin cell DNA, including the activation of oncogenes — a type of gene that, when turned on, can change a normal cell into a cancerous one. But UVA light may be more likely to damage melanocytes, leading to melanoma. Tanning lamps and beds mainly produce UVA radiation.
UV radiation is most intense at the equator and at high elevations, but no matter where you live, your skin absorbs UV radiation whenever you're outdoors unless you wear protective clothing and sunscreen.
Other causes of melanoma
UV light doesn't cause all melanomas, especially those that occur in places on your body that don't receive exposure to sunlight. This indicates that other factors may contribute to your risk of melanoma.
