The Medical Minute: Melanoma - The dark side of the sun

It is generally accepted that sun exposure increases the risk of malignant melanoma, but there is controversy as to how. Statistically, the greater the amount of ultraviolet light and the higher the intensity of exposure, the greater the risk of all skin cancers. Sunburns under age 20 are particularly associated with melanomas.

Skin cancer is kept at bay by a healthy immune system, and ultraviolet light suppresses the skin’s immune system, allowing cancer cells to flourish. Even though tanning booths use only the nonburning UVA part of the ultraviolet spectrum, UVA penetrates deeper into skin and can damage the cells and reduce immune function.

Melanoma can develop anywhere. In men, it is more common on the trunk, head and neck and in women, on the lower legs, but melanomas can arise under fingernails (more common in dark-skinned people) and in the eyes.

Most people have at least one mole. For the most part, moles we are born with are less likely to become melanoma than ones that develop later, particularly moles that show up after age 35 or so. That may seem to make it easy to find bad moles, but as we age, we are susceptible to all sorts of skin changes and growths, some of which are pigmented like melanoma. It can be difficult for the average person to know when to seek a professional opinion about a dark growth on the skin.

People with fairer skin that burns or freckles easily are at greater risk, but people with more than 50 ordinary moles are more likely to develop melanoma. Some moles are abnormal in color or shape, so-called “dysplastic” moles, and these are more likely than normal moles to transform into melanoma. A weakened immune system in general, such as occurs with anti-rejection drugs for an organ transplant or with HIV, is also more likely to fail to stop a melanoma. Living in the south where there is more ultraviolet exposure is associated with more melanoma. Also, having had at least one blistering sunburn as a child makes melanoma more likely.

When a mole develops as an adult or if it or a pre-existing mole grows rapidly, especially in a person with greater risk, it could be melanoma. Other characteristics of melanoma are called the ABCD traits:

• Assymetry - one half of the mole is a different shape, color or texture than the other side.
• Border - the edges are notched, ragged, blurred, or irregular or the pigment spreads into the surrounding areas.
• Color - color is uneven or different shades of black or other colors are present.
• Diameter - rapid change in size or diameter greater than about 6 mm.

Having one or more of the above qualities does not make a diagnosis of melanoma; it makes the diagnosis more likely. Biopsy is the only way to be certain. Deciding which moles to biopsy (take a small piece for diagnosis) or remove entirely should be done by a physician with knowledge and experience in moles and skin cancer.

Melanomas that are removed early when they are superficial are nearly 100 percent curable, just by having them removed. As they grow deeper, it might be necessary to evaluate the lymph nodes near the area of the melanoma to find out if it has spread. Melanoma that has spread is particularly troublesome as the treatment is not as good as treatments for many other cancers. But advances are being made.

True, a little sunlight helps us make vitamin D, but we only need 5-30 minutes of sun exposure on our face and arms two or three times a week, depending on how far away from the equator we live, to get all the vitamin D we need. The rest of the time we should use a broad spectrum UVA/UVB protecting sun block and UV filtering sunglasses when we cannot avoid the sun. Tanning booths increase the risk of cancer in addition to aging the skin more rapidly. Basically, there is no good reason to intentionally expose our skin to ultraviolet light. At the beach, sit under an umbrella, cover up and use sun block. When working outside, wear a hat, light-colored long sleeves and sun block. Where possible, try to avoid being in the sun from 10 a.m. until 2 p.m. when UV intensity is greatest. Children in particular should be protected from the sun and especially from sunburn.

Skin cancer is one of the most preventable cancers. A little effort at prevention and early detection can reduce the risk of dying from melanoma or other skin cancers. For more information on melanoma, go to http://www.cancer.gov/cancertopics/types/melanoma or visit Penn State Milton S. Hershey Medical Center Health Information Library online.

Source: Penn State, by John Messmer