If you take a good look at your skin, you'll probably spot a number of moles—small clusters of pigment-producing skin cells. Most adults have between 10 and 40 moles, and some people, especially those with lighter skin, may have many more.

Moles may change in size and appearance over the years, and in rare instances, a mole may become a melanoma, the most potentially deadly skin cancer.

But if you’re like most people, you don’t usually examine your moles or have a doctor check them periodically to determine whether they're changing in ways that may signal a possible skin cancer.

In fact, a survey of 476 people published in The Journal of Clinical and Aesthetic Dermatology found that only 25 percent of them reported checking their skin monthly and 17 percent reported that they did a skin check just once a year.

So should you or a physician check your skin? If so, how often? Here’s what you need to know about changing moles and skin cancer risk.

Can Any Mole Become 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 can become skin cancers. Some research suggests that having more than 50 common moles may increase one's risk of melanoma.

More worrisome are so-called atypical moles. They often appear during puberty but can pop up throughout life. They’re not skin cancers but can have some features of melanoma, such as irregular borders.

And while the vast majority of these never turn into melanomas,  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.)

Why do some moles change from benign to cancerous? Genetics seems to play a role. And though melanoma can occur in areas that are usually shielded from sunlight, ultraviolet radiation also appears to be a significant factor.

For example, moles exposed to UV radiation, like that from the sun or tanning beds, can mutate, triggering the abnormally rapid cell division that characterizes cancer, according to a 2015 study in the New England Journal of Medicine by Boris C. Bastian, M.D., professor of dermatology and pathology at the University of California, San Francisco, and colleagues.

Most melanomas, however, don't develop from exisiting moles. And rates of the cancer, which increase with advancing age, have been rising for at least 30 years. 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,” says Darrell S. Rigel, M.D., a skin cancer expert at the NYU School of Medicine.

Debate Over Screening

There's been some controversy lately about following the standard advice of getting regular visual skin cancer checks by your doctor.

The U.S. Preventive Services Task Force, an independent expert panel that advises the government on screening tests, has weighed numerous studies and concluded that there's not enough evidence to recommend either for or against routine skin checks. The Task Force also says that while visual skin exams may help detect melanoma, there is no clear evidence that they save lives. (According to the Task Force, routine professional skin checks have the potential to lead to misdiagnosis, overdiagnosis, and adverse effects from biopsies and overtreatment.)

But does this mean you should skip skin exams by your doctor altogether?  David C. Grossman, M.D., the vice chair of the Task Force and a senior investigator at the Group Health Research Institute in Seattle, says that this decision depends largely on you and your doctor's assessments of your own personal risk.

It's important to note that the Task Force didn't look at people at high risk for skin cancer. And the group only reviewed research on exams conducted by primary care health care providers—and didn't assess the potential benefits of having skin checks conducted by dermatologists.

The bottom line:  Our experts recommend that people at high risk should probably see a physician for a skin check at least once a year, preferably a dermatologist, says Jessica Krant, M.D., assistant clinical professor of dermatology at SUNY Downstate Medical Center in Brooklyn, N.Y., and a member of Consumer Reports’ medical advisory board.

Those at very high risk, or with a history of melanoma, should be screened even more often.

Key skin cancer risk factors include a history of sunburns, fair skin, light eyes, red or blonde hair, a family history of melanoma, or a personal history of basal cell or squamous cell cancer. Screenings can also help pinpoint the latter two skin cancers, which are more common, but not as deadly as melanoma.

Even if you are at lower risk, CR's experts say you should have your skin checked periodically by a doctor. Consider asking for a referral to a dermatologist for the exam.

Our experts also consider self checks important. 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.

Don't rely on a skin cancer app to give you the information you need. Research suggests that many are unreliable. And, of course, take steps to protect yourself from excess exposure to UV rays in the first place: Shield your skin when you're outside and avoid tanning beds.