Shedding more light on skin cancers


Summer brings an exodus outdoors, to all the enjoyable recreational activities available and to exposure to sunlight and its radiation.

This radiation, besides causing collagen damage and aging the skin, is the main cause of skin cancer, the most common form of cancer. Even though men are more likely to develop skin cancer, increasing numbers of women in their 20s and 30s are being diagnosed with the disease.

Skin cancer is expected to affect about 1 million Americans this year, equal to all other cancers combined. It is divided into three types: basal cell carcinoma, squamous cell carcinoma and malignant melanoma. Basal cell cancer is the most common. Although not lethal, it will grow into the skin around the cancer, producing slow erosion of the area.

Squamous cell carcinoma, which also is associated with sunlight exposure, will spread to other parts of the body and can be fatal.

Although malignant melanoma also is thought to result from sun

light, it is not clear that all melanoma lesions are directly due to ultraviolet light, since many lesions occur in unexposed areas. Scientists hypothesize that this cancer may be the result of intermittent exposures, rather than total cumulative lifetime exposure (thought to be the cause of the non-melanoma skin cancers).

Dermatologists advise people to see their doctors if they have any skin lesion that grows, changes in color or appearance, itches, bleeds, becomes irritated or will not heal.

Not surprisingly, fair or light-skinned people who sunburn easily have an increased risk of developing skin cancer. But other factors besides skin color may contribute to cancer risk. Most scientists feel that development of skin cancer starts with sunburns and exposure in childhood. Yet many fewer children wear sunscreen or protective clothing than do adults.

Obviously, staying out of the sun is your best protection. However, you can still enjoy the fun if you take a few simple precautions.

Minimize your sun exposure between 10 a.m. and 2 p.m., the period when the sun's rays are most harmful. Loose clothing and a hat provide important protection. For the parts of you not covered, a sunscreen is critically important. A sun block with a sun protection factor (SPF) of 15 is the minimum protection you need. The higher the SPF number, the more protection.

Also, sunlight is known to reduce the immunity, or infection-fighting capability, in people exposed to its rays. Although more information is needed, the evidence so far suggests that lowered immunity occurs even in the presence of sunscreens and natural protection from melanin.

Adults who take medications should inquire as to whether their prescriptions increase sun sensitivity. Hormone therapy as well as drugs commonly used for heart disease and other illnesses may result in severe problems when exposed to sunlight. Dr. Matanoski is a physician and epidemiologist at the Johns Hopkins School of Hygiene and Public Health. She is founding director of its Institute for Women's Health Research and Policy.

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