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.