The Sun and Skin Cancer

Posted By SHL Librarian

Presented by: Sumaira Z. Aasi, MD
Clinical Associate Professor, Dermatology
October 10, 2012

Skin is the largest organ of the human body. It serves a tremendous immune defense system designed to protect you from the environment, regulates internal temperature, and keeps out infection. It’s also a window to your overall health.

Because it is bombarded by so many external elements, skin reflects changes that can be noticed and tracked, from innocuous freckles and moles to dangerous forms of skin cancer. In fact, skin cancer is at epidemic levels, says Sumaira Z. Aasi, MD, a clinical associate professor of dermatology, who spoke at a presentation sponsored by Stanford Hospital Health Library.

Skin cancer is the most common form of cancer in the United States. More than 1.3 million cases are diagnosed each year—20 percent of all Americans. It is usually curable if caught early and treated appropriately, she says.

Sun damage is the primary cause of skin cancer, intensified by the depletion of the ozone layer, an outdoors lifestyle, minimal clothing, and a population that is living longer. People most at risk have fair skin, blue eyes, and blonde or red hair. Though genetics and other environmental exposures can also cause skin cancer, unprotected sun exposure is the biggest cause of basal cell carcinoma, squamous cell carcinoma, and melanoma.

“The more exposure to the sun, the higher the incidence,” Dr. Aasi says. “No one wants to think about skin cancer while doing activities you enjoy, but it is really all about sun exposure. The effect is cumulative, so even if you are conscientious about covering up and using high SPF protection now, the damage started years ago, with exposure when you were young.”

Cancer Development
Exposure to the sun’s ultraviolet radiation causes mutations in the DNA of skin cells. Normally your immune system is programmed to get rid of mutated cells, which is what happens when you get a sunburn and the skin peels—your body is getting rid of the damaged skin cells. As we age, however, the immune system does not register these changes as well, and some mutations slip through the protective system. The mutations cause the cells to grow out of control and become cancerous cells.

“You may not think you have sun damage, but take a look at your arm and compare it to a part of your body that is seldom exposed, like your inner thigh or the underside of your arm,” Dr. Aasi says. “It’s an obvious demonstration of how much you have been exposed to the sun.”

Skin cancer develops primarily on areas of sun-exposed skin, including the scalp, face, lips, ears, neck, chest, arms, and hands, but it can also form on areas that rarely see the light of day. Look for a bump or mark that bleeds, changes color, doesn’t heal, or gets bigger over time, Dr. Aasi says. “No one knows your body as well as you do, so be your own best advocate and keep track of any changes.”

Basal cell carcinoma is the most common form of skin cancer. It’s slow growing and rarely spreads, so it is rarely fatal but can be highly disfiguring if allowed to grow. Look for a red, scaly patch that gets bigger or a pimple with small blood vessels.

Squamous cell carcinoma is the second most common form of skin cancer. It starts off looking like a scaly patch, flat lesion, or red nodule. Actinic keratosis are precancerous growths that also result from sun exposure and can sometimes develop into squamous cell carcinomas. These can be treated very easily in the office without surgery.

Melanoma is the most dangerous form of skin cancer because of its ability to spread into the lymph nodes. Melanoma arises from melanocytes, the cells that provide color to the skin, so it often appears black or brown but can be red or pink as well.

Skin Cancer Treatment
Usually a physician will biopsy a skin sample to determine if a lesion is a skin cancer. If it is cancer, there are multiple treatment options depending on the location and size, such as simple scraping (curettage) and burning (electrodesiccation) and as well as surgical excision. Typically surgery involves cutting the growth, along with a margin of nearby skin to make sure all the cancer cells are removed.

In certain situations an option called Mohs micrographic surgery allows surgeons to remove the cancer while sparing healthy adjacent tissue and examine the margins right away under a microscope while the patient waits. The procedure is used mostly for basal cell and squamous cell carcinoma, and has a 99 percent cure rate for most first-time cancers.

“The technique offers the highest cure rate for skin cancer removal while minimizing the size of the resulting scar,” says Dr. Aasi. “It allows us to be extremely precise, so we can preserve surrounding healthy tissue and save as much skin as possible.”

The procedure requires a special laboratory for analysis of the skin, and Dr. Aasi advises that patients check to make sure the dermatologist using Mohs has been trained through a fellowship. Stanford’s Redwood City dermatology clinic is home to one of the leading Mohs surgery programs in the region.

Cancer Prevention
The most important step to prevent the development of skin cancer is to protect your skin, Dr. Aasi says. Use sunscreen with an SPF of 30 or higher, with broad spectrum UVA and UVB protection. Use sunscreen before you go outside, and be sure to use enough.

“Most people think they are protected but they have not used the proper amount or reapplied it sufficiently,” she says. “Use about a shot glass full and remember to cover your feet, back of neck, ears, and near your eyes. There’s no such thing as waterproof sunscreen, so reapply it when you get wet or sweat. Think of it as paint —apply and then reapply a second coat to get good coverage.”

Cover yourself with loose, lightweight clothing, use a broad-brimmed hat (baseball caps do not provide coverage to the back of the neck or ears), and try to do outdoor activities in the morning or late afternoon—not during prime midday sun.

“There’s no such thing as a safe tan,” she adds. “Artificial radiation from tanning beds is as bad or worse than natural sunlight. The sun might feel good, but it is dangerous.”

Dr. Aasi also suggests you start seeing a dermatologist in your 30s to establish a baseline to track any changes in your skin and to be diligent about doing self-exams on a regular basis.

About the Speaker
Sumaira Aasi, MD, is a clinical associate professor of dermatology specializing in skin cancer and Mohs surgery. She received her MD from Northwestern University Feinberg School of Medicine and did her internship at the University of Chicago Hospitals and her residency at Northwestern University’s McGaw Medical Center. She completed her fellowship in Mohs micrographic surgery and advanced cutaneous oncology at Yale University. Dr. Aasi is Board Certified by the American Board of Dermatology.

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About Dr. Aasi

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Mohs Surgery Clinic

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