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Skin cancer is the most common type of cancer in the U.S., and it has increased dramatically in the last 50 years. Melanoma, the deadliest form, is expected to rise by 6% in 2025, and the incidence of melanoma in people under 30, especially women, is increasing faster than in any other age group.
Excessive sun exposure is the leading cause of skin cancer, which is why it most commonly occurs on the face, scalp, ears, neck, upper chest and hands. “These are the areas that receive the most cumulative sun exposure over a person’s lifetime,” says Dr. David C. Reid, professor and chair of dermatology at the Rush University Medical Center in Chicago.
But skin cancer can also develop in areas that aren’t regularly exposed to the sun, including the palms of the hands, soles of the feet, genitals, buttocks, eyelids, in the skin under the nails, and inside the mouth or nose.
People are often surprised that certain areas of the body that they think are protected from the sun—such as the scalp and the tops of the feet—can still get significant exposure to the sun’s ultraviolet rays, says Dr. Kathleen Suozzi, chief of surgical dermatology at the Yale School of Medicine and Yale Cancer Center. But, she says, “while UV radiation is the leading cause of most skin cancers, it’s not the only factor.”
What else causes skin cancer, besides the sun?
Genetic factors, immunosuppression (especially for those who have had organ transplants), and chronic inflammation can all raise a person’s risk. So can past injuries; skin cancer can develop in previously injured areas, such as wounds or scars, without sun exposure, Reid says.
Occupational exposure to certain types of chemicals—such as those encountered by firefighters and industrial workers—can also increase the risk of developing skin cancer, he adds.
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Viruses, such as the human papillomavirus (HPV), are a common cause of genital skin cancers on the vulva, vagina, anus, and penis. “HPV is a super common virus—and it’s not just sexually transmitted,” says Dr. Anthony Rossi, a dermatologist and Mohs surgeon at Memorial Sloan Kettering Cancer Center and chief medical officer at the skin health company Joya. It can also spread through non-sexual contact with infected skin.
And indoor tanning is a major contributor to skin cancer. Experts believe that the increased popularity of tanning beds and artificial sunlamps is a main reason why melanoma is rising among young people. People who have tanned indoors at any point in their lives have a 29% higher risk of developing basal cell carcinoma and an 83% increased risk of developing squamous cell carcinoma compared to people who never have, according to the Skin Cancer Foundation.
The three main types of skin cancer and where they’re found
Basal cell carcinoma is the most common form of skin cancer, and it’s typically related to chronic sun exposure. That’s why it’s often found on the face (including the nose, lips, and cheeks), ears, and neck, says Dr. Susan Massick, associate clinical professor of dermatology at The Ohio State University Wexner Medical Center. While it’s “not particularly aggressive, it can become more problematic if it’s ignored, untreated, or allowed to progress.”
Squamous cell carcinoma is the second-most common kind, and it’s typically found on the face, ears, neck, lips and backs of the hands, though it can appear anywhere on the body. “Squamous cell carcinoma favors sun-exposed areas, but can also arise in scars, chronic ulcers, or from viruses, in sun-protected areas,” Reid says. While it’s highly treatable when identified in an early stage, squamous cell carcinoma can spread to surrounding tissues if it’s not addressed.
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Melanoma, which is the third most common type of skin cancer, tends to also occur in sun-exposed areas, particularly on the chest, torso, and back in men and the legs in women, Rossi notes. But it can also develop in non-sun-exposed areas such as the mucous membranes in the nose and mouth and the eye, Massick says. It’s the deadliest form of skin cancer because it can spread to other areas of the body if it’s not detected and treated early.
How to prevent skin cancer
Given the connections between skin cancer and sun exposure, it’s important to use a broad-spectrum sunscreen on your skin with an SPF of 30 or higher on a daily basis throughout the year. When spending time outside, reapply sunscreen every two hours, and be sure to apply enough: the amount should fill a shot glass for the whole body, plus two to three fingertips worth on the face and neck, Rossi says.
When spending long periods of time outdoors, the Skin Cancer Foundation also recommends wearing UPF protective clothing, including wide-brimmed hats, and sunglasses that block at least 99% of UVA and UVB light.
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Use these strategies when you’re driving, too, because UVA penetrates through window glass, Rossi says. You may even want to wear driving gloves to protect the skin on your hands.
“It’s also helpful to check the daily UV Index, which is included in smartphone weather apps,” says Reid. “A score of 3 or higher means it’s time to take precautions” such as seeking shade during the midday hours.
Always steer clear of tanning beds, Suozzi advises, and avoid UV exposure in gel manicures.
How to spot potential signs of skin cancer
The key is to do monthly skin self-exams, making a concerted effort to check out the skin all over your body, including on your back, scalp, and genital areas. (You may want to enlist a partner’s help for these hard-to-see areas—or use mirrors strategically.)
Keep in mind: “If you have light-colored hair, red hair, or thinning hair, it doesn’t offer as much photoprotection,” Rossi says. That’s why it’s important to continuously part the hair during skin checks so you can see as much of your scalp as possible.
And don’t forget to examine your nails and the bottoms of your feet, Reid says. A skin cancer subtype called acral lentiginous melanoma tends to appear on the palms of the hands, soles of the feet, or under the nails, “and it is more common in individuals with darker skin tones.”
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Many people have heard of the ABCDE’s for identifying suspected melanoma in moles or pigmented spots: A is for asymmetry (meaning one half looks different from the other), B is for border (the spot has an irregular or poorly defined border), C is for color (meaning the spot has color variations, such as shades of tan, brown, black, white, red, or blue), D is for diameter (spots that are larger than the size of a pencil eraser can signal melanoma), and E is for evolving, which means the spot is changing in size, color, or shape.
The warning signs are different for other forms of skin cancer. Basal cell carcinoma may look like a pearly bump, a sore that doesn’t heal, or a pink, scaly patch, Massick says. “Squamous cell carcinoma might also appear as a pink, scaly patch, a wart-like growth or a rough, thickened area of skin that bleeds, scabs, or crusts”—and doesn’t heal.
If you develop any of these skin signs and they persist for a couple of months, see a dermatologist. “It’s not just moles—any persistent skin change should raise suspicion,” says Suozzi.
In general, it’s wise to see a dermatologist once a year for a full-body skin check, Rossi says. Your doctor can then do a biopsy of anything unusual and send it to a lab to diagnose or rule out cancer. The key is to catch any abnormal spots early—wherever they arise.
