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Recognizing and treating basal cell carcinoma

MAY 2006

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It’s the most common skin cancer and the least dangerous — but it’s far from a trivial matter.

From the Harvard Women’s Health Watch, May 2006

With summer around the corner, our thoughts and plans naturally turn to outdoor activities and the opportunity to bask in the warmth of the sun. But there’s a dark side to the time we spend in the sun — it’s called a tan. Despite its association with prosperity, good looks, and good health, a tan in reality is a sign that the sun has damaged the skin cells. For some people, such damage can result in skin cancer. The sun is the chief cause of more than 1.3 million skin cancers each year in the United States.

There are three main types. Melanoma is probably the most familiar — not because it’s common but because it’s so deadly. It accounts for only 4% of skin cancers but 75% of skin cancer deaths. A second type, squamous cell carcinoma, occurs three times more often than melanoma. Although it’s less serious, it can metastasize and cause extensive damage. About 3%–4% of people with squamous cell carcinoma die from the disease.

By far the most common skin cancer, and the subject of this article, is basal cell

carcinoma. Figures from the American Cancer Society suggest that there are nearly one million new basal cell skin cancers each year. The good news is that basal cell carcinoma rarely metastasizes and can easily be treated and cured when discovered early. The bad news is that removing even this least dangerous type of skin cancer can be potentially disfiguring, especially if it has grown for a while or involves cosmetically important areas.

About basal cell carcinoma

Basal cell skin cancers develop from cells that line the bottom of the skin’s top layer (epidermis). They almost always occur in areas exposed to the sun: 80% show up on the head and neck, and most of the rest on the trunk, arms, and legs. The face, especially the nose, is particularly vulnerable.

The characteristics and location of basal cell carcinoma vary somewhat with the type, although many are a mixture of types. The most common form — nodular — usually shows up as a shiny bump, generally on the face, scalp, ears, or neck. It may bleed easily. And it often ulcerates and crusts over, which may create the illusion that it’s healing. Superficial basal cell carcinoma usually occurs on the trunk, especially the back, as a red, scaly, sometimes itchy spot (it may have flecks of dark pigment). It’s often mistaken for a patch of dermatitis. A rarer and more aggressive type (morpheaform) has a waxy white or yellow scarlike appearance and poorly defined borders.

Basal cell carcinoma may start off looking like a harmless blemish (see photos). Let a dermatologist take a look at anything that won’t go away, bleeds easily, or won’t heal — or that heals, breaks down again, then heals again.

Photos provided by the Skin Cancer Foundation, New York, NY

Who’s at risk?

Basal cell carcinoma is slow-growing and occurs mostly in people over age 55. It’s more common in men than in women, although the incidence in younger women is rising. Sun exposure is the biggest risk factor. We don’t know precisely why one person gets squamous cell carcinoma and another gets basal cell, but it probably has to do with greater and lesser degrees of sun damage over time and the intensity of the sun’s rays.

People with fair skin, blond or red hair, and blue, grey, or green eyes are at greatest risk. Other risk factors include a history of ionizing radiation therapy to treat acne, eczema, or psoriasis; chronic immunosuppression for organ transplantation; long-term use of oral glucocorticoids (steroid drugs); and a history of previous skin cancer of any type. People who have had multiple basal cell cancers are at greater risk for squamous cell carcinoma and melanoma.

Scientists are only beginning to understand how sunlight causes basal cell carcinoma. One possibility is that the sun’s ultraviolet rays cause inflammation and increased levels of COX-2, an enzyme implicated in the development of cancer. Certain gene mutations may also be involved.

A tan wasn’t always fashionable

The idea that light-skinned people look better with a tan reportedly dates back to the 1920s, when the French fashion designer Coco Chanel returned from a Riviera vacation sporting a bronzed look. Fashion mavens took note, and the tan soon became a sign of class and style. (Ironically, in the 19th century and earlier, middle-class and upper-class people avoided having a tan because it suggested outdoor labor, which implied low social rank.) Having “some color” is still socially desirable, despite overwhelming evidence of its considerable risks. In China, Japan, and other Asian nations, many women use parasols when they’re out in the sun in an effort to maintain a fair complexion — a fashion that makes far more health sense than a tan.

Diagnosis and treatment

Skin cancers can often be diagnosed by appearance, but a biopsy is needed to confirm the diagnosis.

The goal of treatment is to remove the cancer completely with the least possible cosmetic damage. The options, which include cryosurgery, surgical removal, radiation, and topical creams have rarely been compared in controlled trials, but in properly selected patients, each has a cure rate of 90% or more for first-time cancers.

Surgical approaches. Simple excision, cryosurgery (freezing), and electrosurgery (which involves scraping and burning) work well for low-risk types — mostly small nodular or superficial ones that appear almost anywhere except the face (and possibly the neck and ears) and aren’t aggressive. Larger cancers, morpheaform ones of any size, and those on the face and other structurally or cosmetically sensitive areas are considered high-risk. These are best treated with surgical removal that allows the surgeon to check during the procedure to make sure she or he has removed the entire cancer and just enough healthy tissue to get cancer-free margins. This cuts the risk of a recurrence while giving the best possible cosmetic result.

These days, the usual first choice for removing high-risk basal cell skin cancers is Mohs micrographic surgery (named after its developer, Dr. Frederic Mohs). The surgeon removes the cancer layer by layer, examining each one microscopically until the margin around the cancer is free of cancer cells. It’s technically exacting and takes longer than other procedures, but the cure rate approaches 100%. (You can learn more about Mohs surgery on our Web site.)

Nonsurgical techniques. Radiation therapy is noninvasive, painless, and often the best choice if you are not a candidate for surgery. But it requires repeat visits, and there’s some risk that the cancer will be more aggressive if it recurs. Radiation therapy generally isn’t recommended for patients under age 50 because of the risk of developing a new skin cancer at the site in 10–15 years. Low-risk superficial basal cell carcinoma can be treated with ointments, including 5-FU and imiquimod (Aldara), which are applied daily for several weeks or months. Cure rates are mixed.

The trouble with basal cell carcinoma

Basal cell skin cancer usually isn’t life threatening and it rarely spreads to other parts of the body, but it can cause trouble in its immediate vicinity. That’s because it tends to grow downward and outward below the skin’s surface. Consequently, there may be much more to it than strikes the eye, and a first pass at removing it (area within the dotted line) may not get it all.

Protecting your skin from sun damage

The sun’s rays prematurely age the skin and cause wrinkles as well as skin cancer. For these reasons, a broad-spectrum sunscreen is the most important skin product you can buy. “Broad spectrum” means that it provides protection from the two main types of ultraviolet (UV) radiation, UVA and UVB. UVB is the chief cause of sunburn. The sun protection factor (SPF) number on the label indicates how well a sunscreen protects you from sunburn.

But sunburn protection doesn’t equal skin cancer prevention. UVB was once considered the main skin cancer culprit, but experts now believe UVA is just as important.

Unfortunately, not all sunscreens contain UVA blocking agents, and for those that do, there’s no rating system like the SPF numbers. (The FDA is still working on this.) For now, make sure that your sunscreen contains agents that help protect you from both UVA and UVB. These include titanium dioxide, zinc oxide, avobenzone (Parsol 1789 or methoxydibenzone), dioxybenzone, oxybenzone, sulisobenzone, and methyl anthranailate. Mexoryl, which some experts say provides the best UVA protection, is under FDA review and not yet available in the United States.

Our most common mistake with sunscreen is not using enough. Most people apply only a quarter of the amount they need, which “converts an SPF of 30 into an SPF of about 6,” says Carl Schanbacher, a Mohs surgeon at Dana-Farber Cancer Institute in Boston. How much sunscreen is enough? Dr. Schanbacher suggests the following amounts: 1 teaspoon for the head and neck, 1 teaspoon for each arm, 1–3 teaspoons for the trunk, and at least 1 teaspoon for each leg. That may seem like a lot, but that’s what you need.

Apply sunscreen — use an SPF of at least 15, and preferably 30 — about 30 minutes before going out, so that it absorbs well and becomes fixed to the skin. Reapply it every two hours and after swimming; this is important because some of the active ingredients break down in the sun. But sunscreen isn’t a carte blanche to sunbathe all day. Try to avoid the sun when UV radiation is most intense (10 a.m.–4 p.m.). Also, wear a broad-brimmed hat that protects your ears and neck (a baseball cap isn’t a good choice), sunglasses, and long-sleeved clothing made of tightly woven fabric. You can buy sun-protective clothing. Some carry an ultraviolet protection factor (UPF) rating that indicates how much UV radiation the fabric blocks. You can also wash UV protection into your clothes with a laundry additive called SunGuard.