Skin Cancer: Types, Risk Factors, Prevention, and More

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Skin Cancer: Types, Risk Factors, Prevention, and More

With the summer upon us, it’s only normal to want to get out and enjoy the great outdoors. But before you go, it’s important to protect yourself against the sun to help avoid skin cancer. It’s also important to realize that skin cancer can occur on areas of your body that may not usually be exposed to sunlight, so you should learn how to spot suspicious signs and symptoms and know when to seek medical attention. The good news about skin cancer is that if it’s caught early, it can be treated and eliminated entirely. Here are some skin cancer facts that can help you stay safe.

What is skin cancer?

Unfortunately, most of us are all too familiar with cancer. Chances are, you, a family member, or a friend has or has had cancer. Skin cancer happens to be the most common type of cancer in the United States. One reason for this is that the skin is the largest organ (yes, skin is an organ!) in the body. The Skin Cancer Foundation defines skin cancer as “the out-of-control growth of abnormal cells in the epidermis, the outermost skin layer, caused by unrepaired DNA damage that triggers mutations.” Mutations cause skin cells to multiply rapidly and become malignant (cancerous).

Skin cancer mostly develops on skin that is exposed to the sun’s ultraviolet (UV) light. UV rays are an invisible type of radiation that comes from the sun, but they can also come from sunlamps and tanning beds. These UV rays damage skin cells. Of note, you can still be exposed to UV rays even during cloudy and cool days; they can be reflected off water, snow, sand, and even cement. UV rays are strongest in the United States between 10 a.m. and 4 p.m. daylight saving time.

What are the different types of skin cancer?

There are four main types of skin cancer: basal cell carcinoma, squamous cell carcinoma, melanoma, and Merkel cell carcinoma.

Basal cell carcinoma

Basal cell carcinoma (cancer) is one of the most common types of skin cancer. It starts in the skin’s outermost layer, called the epidermis.

Where it’s usually found

Areas often exposed to the sun, such as the face, ears, scalp, neck, shoulders, and back.


  • Open sore that doesn’t heal, or that oozes or bleeds
  • Reddish area on the skin
  • A shiny bump that is pearly or clear, pink, red, white, or brown

Squamous cell carcinoma

Squamous cell carcinoma is another common type of skin cancer that forms in the squamous cells (cells in the middle and outer layers of the skin). Squamous cell carcinoma is usually not life-threatening, but if it’s not treated, it can grow and spread to other parts of the body.

Where it’s usually found

Areas exposed to the sun, including the face, ears, neck, scalp, and hands.


  • Firm, red growth
  • Flat sore with a scaly crust
  • Brown spot that looks like an age spot
  • A sore that develops in an old scar
  • A red sore inside the mouth


Melanoma is less common than other types of skin cancer, but it’s also more dangerous, according to the American Cancer Society, because it’s much more likely to spread to other parts of the body. Melanoma begins in melanocytes, which are the cells that give the skin its color.

Where it’s usually found

The face, neck, chest, back, and legs; can also occur on the palms of the hands, soles of the feet, under the nails. Can rarely occur in the eyes, mouth, and genitals.


  • A large brown area that looks like a mole
  • A mole that changes size, shape, or color
  • A dark lesion on the palm, fingertips, soles, or toes, or on mucous membranes lining the mouth, nose, vagina, or anus

Merkel cell carcinoma

Merkel cell carcinoma is a rare but aggressive skin cancer that starts in skin exposed to the sun, typically on the head, scalp, neck, arms, legs, and trunk. Merkel cells are found in the top layer of the skin, close to nerve endings. This type of cancer is linked with the Merkel cell polyomavirus and most often develops in older people.

Where it’s usually found

The head, eyelids, neck, trunk, arms and legs.


  • Firm, flesh-colored or bluish-red nodule on the face, head or neck

Risk factors for skin cancer

Anyone can get skin cancer, but certain factors increase the risk, according to the CDC:

  • A lighter skin color
  • Skin that freckles, reddens, or burns easily
  • Blue or green eyes
  • Blonde or red hair
  • Certain types and a large number of moles
  • A family history of skin cancer
  • A personal history of skin cancer
  • Older age
  • Exposure to radiation
  • A weakened immune system

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Practicing sun safety

Make sure to protect yourself from UV rays all year, not just in the summer, and not just on sunny days. Pay attention to the UV index, which forecasts the strength of UV rays each day. A UV index of 3 or higher means that you need to be especially careful. Here’s how:

  • Stay in the shade between 10 a.m. and 4 p.m.
  • Use a broad-spectrum (UVA/UVB) sunscreen with an SPF of at least 15 or higher every day (even on cloudy days)
  • Don’t use tanning beds, booths, or sunlamps
  • Wear clothing that covers your arms and legs. If you are outdoors often, consider wearing “sun safe” clothing (learn more here).
  • Wear wrap-around sunglasses that block both UVA and UVB rays.
  • Wear a hat with a wide brim to shade your face, head, ears, and neck.

Medicine and sun sensitivity

Some medicines can make you more sensitive to sunlight and cause your skin to burn easily or to develop a rash. This is known as photosensitivity. These medicines include:

  • Certain antibiotics (e.g., ciprofloxacin, doxycycline, tetracycline)
  • Antihistamines (e.g., cetirizine, diphenhydramine, loratadine, promethazine, cyproheptadine)
  • Diuretics (e.g., hydrochlorothiazide, chlorthalidone, chlorothiazide, furosemide, triamterene)
  • Oral contraceptives and estrogen
  • Retinoids (e.g., acitretin, isotretinoin)
  • Statins (e.g., simvastatin, atorvastatin, lovastatin, pravastatin)
  • Sulfonylureas (e.g., glipizide, glyburide, glimepiride)

This isn’t a complete list of medicines, so make sure you know which medicines, if any, that you take that could cause photosensitivity. If you develop a severe sun burn, rash, fever, chills, headache, or nausea, contact your healthcare provider.

Check for possible signs of skin cancer

Most skin cancers are treatable if caught early. The key, though, is picking up on signs early on. Ideally, you should check your own skin once a month, especially if you have any of the skin cancer risk factors mentioned above.

To check your skin, the American Cancer Society recommends being in a well-lit room with a full-length mirror. Have a partner, spouse, or friend check hard-to-see areas for you, such as your back or your scalp. And the best time to do a skin check is after a shower or a bath. For steps and pictures of what skin cancer might look like, visit the American Cancer Society’s website. Be sure to follow up with your doctor or dermatologist if you come across anything that looks worrisome, or even if you’re not sure. Better safe than sorry!

Also, talk with your doctor or dermatologist about how often you need a professional skin check. Many people have yearly skin checks with a dermatologist.

Skin cancer and diabetes

Some research indicates that people with diabetes may have a higher risk of skin cancer. For example, a study published in 2013 in the journal Diabetes Care found that duration of diabetes was “significantly and positively associated with the prevalence of cancers of all sites and of some specific sites,” as was the use of insulin. Another study that looked at skin cancer patients with diabetes in Taiwan found a higher incidence and risk of developing skin cancer in older adults with diabetes.

Of interest, a 2021 study published in the Journal of the American Academy of Dermatology showed that taking metformin was associated with a decreased risk of basal cell carcinoma, and that metformin could be a chemoprotective agent (a medicine that helps reduce the side effects of chemotherapy) for people at high risk of squamous cell carcinoma.

Want to learn more about diabetes and skin care? Read “Diabetes and Your Skin,” “The Prescription for Dry Winter Skin” and “Summertime Skin Care.”

Amy Campbell, MS, RD, LDN, CDCES

Amy Campbell, MS, RD, LDN, CDCES

Amy Campbell, MS, RD, LDN, CDCES on social media

A Registered Dietitian and Certified Diabetes Educator at Good Measures, LLC, where she is a CDE manager for a virtual diabetes program. Campbell is the author of Staying Healthy with Diabetes: Nutrition & Meal Planning, a co-author of 16 Myths of a Diabetic Diet, and has written for  publications including Diabetes Self-Management, Diabetes Spectrum, Clinical Diabetes, the Diabetes Research & Wellness Foundation’s newsletter,, and

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