Could That Old Mole Be Skin Cancer?

Can All Moles Cause Skin Cancer?

Common moles are those we’re born with or develop until about age 40. They can change or even disappear over the years, and very rarely become skin cancers. But according to the National Cancer Institute, having 50 or more puts people at higher risk of melanoma­—although brand-new research published in JAMA Dermatology has called that into question.

So-called atypical moles often appear during puberty but can pop up throughout life. They’re considered benign (not skin cancers) but may have some features of melanoma, such as irregular borders.

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Most atypical moles don’t become melanomas, but they are more likely than common moles to become cancerous. Having five or more atypical moles is linked to a higher than normal risk of “thick,” or more advanced, melanoma. (Many melanomas start as pigmented moles, but the two more common skin cancers, basal cell and squamous cell carcinoma, don’t. They arise on their own from normal skin.)

The mechanism behind a mole’s change from benign to cancerous may be genetic in some cases. And though melanoma can occur in areas that are usually shielded from sunlight, ultraviolet radiation seems to be a significant factor. In a study published in the New England Journal of Medicine, Boris C. Bastian, M.D., Ph.D., professor of dermatology and pathology at the University of California, San Francisco, and colleagues found that a mole exposed to UV radiation (like that from the sun or tanning beds) can mutate, triggering the abnormally rapid cell division that characterizes cancer.

Pros and Cons of Checking for Skin Cancer

Many experts and organizations, such as the American Academy of Dermatology, recommend that we all regularly do skin self-checks and have screenings by a physician to monitor moles. But in 2009 the U.S. Preventive Services Task Force, an independent expert panel, found insufficient evidence to recommend for or against screenings at the doctor’s office or at home. Instead, it suggested that doctors be alert for suspicious skin growths during physical exams.

What does that mean for you? Melanoma rates have been rising rapidly for at least 30 years, and risk increases with age. Unnoticed, melanoma can grow and spread quickly, so experts agree that finding it early is key. “A melanoma the size of a dime has a 50 percent chance of having spread,” notes skin cancer expert and AAD spokesman Darrell S. Rigel, M.D.

And the task force hasn’t assessed the value of home or doctor’s office skin screenings for those at high risk. That includes anyone with a history of sunburns, fair skin, light eyes, red or blonde hair, a family history of melanoma, and/or a personal history of basal cell or squamous cell cancer. Screenings can also help pinpoint the latter two skin cancers.

For those reasons, our experts advocate regular skin exams by a dermatologist. “Even low-risk individuals should be screened annually,” says Jessica Krant, M.D., M.P.H., clinical assistant professor of dermatology at SUNY Downstate Medical Center in Brooklyn, N.Y., and a member of Consumer Reports’ medical advisory board. “High-risk people may need two or more yearly screenings.”

The task force recommendations “don’t mean people should avoid regular skin self-checks or skin exams. They are driven by cost-effectiveness and refer to screenings by a primary care provider, not a dermatologist­—who is more likely to identify potentially dangerous growths,” Krant adds.

With do-it-yourself skin checks, Krant recommends a monthly or every other month schedule. (A study in the journal Archives of Dermatology found that 44 percent of melanomas were discovered by patients.) Use the commonly accepted ABCDE method. And if you spot new moles or are unsure whether a mole's changes may be meaningful, see a dermatologist. Sometimes, a melanoma may not resemble other melanomas in shape, color, or size, says Scott W. Fosko, M.D., chair of dermatology at the Mayo Clinic in Jacksonville, Fla. For example, he says, the unusual amelanotic melanoma has little to no color.

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