How Many Different Types Of Skin Cancer Are There?

This question originally appeared on Quora. Answer by Keck Medicine of USC.

You may have heard the word melanoma tossed around a lot, but what other types of skin cancer are there?

With more than 5.4 million people diagnosed in the United States each year, skin cancer is the most common cancer people get. According to the latest reports, each year there are more new cases of skin cancer than the combined incidence of cancers of the breast, prostate, lung and colon.

Melanoma cancer

Melanoma cancer (also known as malignant melanoma and cutaneous melanoma) only accounts for one percent of all cancers, but it causes the majority of deaths from cancer because it can spread to other parts of the body easily. According to the American Cancer Society, about 87,110 new melanomas will be diagnosed (about 52,170 in men and 34,940 in women) this year.

This cancer begins in melanocytes, specialized skin cells that produce the protective skin-darkening pigment known as melanin. Some melanomas do not make melanin and can appear pink, tan or even white.

Melanomas can develop anywhere on the skin, but they’re more likely to start on the chest and back in men and on the legs in women. They can also occur on the neck and face. In addition, they can form on other parts of the body, such as the eyes, mouth, genitals and anal area, but those are more uncommon.

Basal cell carcinomas and squamous cell carcinomas

While melanoma often gets the most coverage, there are two other major types of skin cancer: basal cell carcinoma (approximately 4 million cases per year in the United States) and squamous cell carcinoma (approximately 700,000 cases per year in the United States). Often grouped together as non-melanoma skin cancers, these two types are much more common than melanoma cancer. They are unlikely to spread to other parts of the body, but they may be locally disfiguring if not treated early.

Basal cell carcinomas are abnormal, uncontrolled growths or lesions that arise in the skin’s basal cells, which line the deepest layer of outermost layer of the skin. They often look like open sores, red patches, pink growths, shiny bumps or scars and usually are caused by sun exposure.

Warning signs include:

• Flat, firm, pale or yellow areas, similar to a scar
• Raised reddish patches that may be itchy
• Small, pink or red, translucent, shiny, pearly bumps, which might have blue, brown or black areas
• Pink growths with raised edges and a lower area in their center, which may contain abnormal blood vessels
• Open sores (which may have oozing or crusted areas) that don’t heal or that heal and then return
• Basal cell cancers are often fragile and might bleed after shaving or after a minor injury. If you have a sore or a shaving cut that doesn’t heal after a week, it would be wise to contact your doctor.

Squamous cell carcinomas usually occur on sun-exposed areas of the body such as the face, ear, neck, lips and back of the hands. Sometimes they may form in the skin of the genital area. They can also develop in scars or skin sores. Warning signs include:

• Rough or scaly red patches, which may crust or bleed
• Raised growths or lumps, sometimes with a lower area in the center
• Open sores (which may have oozing or crusted areas) that don’t heal or that heal and then come back
• Wart-like growths

Other types of skin cancer

Unusual types of skin cancer include Merkel cell tumors. Merkel cell carcinoma starts when cells in the skin called Merkel cells start to grow uncontrollably. This type of cancer can grow quickly and can be hard to treat if it spreads beyond the skin.

Dermatofibrosarcoma protruberans is another rare skin cancer, which begins in the middle layer of skin, the dermis. The cancer tends to grow slowly and seldom spreads to other parts of the body.

The basic facts

Cancer occurs when normal cells go through a transformation and grow and multiply without normal controls. As these cells multiply, they form a swollen tissue called a tumor, which may be cancerous if it is malignant. This means that they will invade neighboring tissues — especially lymph nodes — because of their unleashed growth. They overwhelm the surrounding tissues by taking their space and feeding on their essential oxygen and nutrients.

Skin cancers start as precancerous lesions. These precancerous lesions are changes in skin that are not cancer, but could become cancer over time. Doctors refer to these changes as as dysplasia. Among some dysplastic changes that occur in skin that you need to keep an eye on are:

• Actinic keratosis is a red or brown, scaly, rough skin area, which can develop into squamous cell carcinoma.
• A nevus is a mole, and abnormal moles are called dysplastic nevi. These can potentially develop into melanoma over time. Moles are simply growths on the skin that rarely develop into cancer. If a mole on your body looks different from the others, you should contact your health care provider to take a look at it.
• Dysplastic nevi, or abnormal moles, are not cancer, but they can become cancer. People sometimes have as many as 100 or more dysplastic nevi, which are usually irregular in shape. Some may be flat or raised, and the surface may be smooth or rough. They are often large, at a quarter-inch across or larger, and are typically of mixed color, including pink, red, tan and brown.

Keeping cancer in check

Chronic exposure to the sun or intermittent sunburns can lead to skin cancer. Skin cancer risk doubles with five or more sunburns in a lifetime, but just one bad sunburn can double the risk of melanoma. While skin cancer is uncommon in African Americans, Latinos and Asians, it can also be more deadly because they are often diagnosed later in the course of the disease.

“The cumulative ultraviolet radiation through your entire life determines your risk for skin cancer,” explained Ashley Wysong, MD, MS, assistant clinical professor of Dermatology at Keck School of Medicine and director of Mohs and Dermatologic Surgery at USC Dermatology at Keck Medicine of USC.

It’s important to examine your skin regularly. You should report any changes in an existing mole (color, size, border, irregularity) or any new moles to your physician. People with fair complexion have the highest risk of developing skin cancer, but everyone should avoid the sun and practice safety measures to protect their skin.

The American Cancer Society recommends the “Slip, Slop, Slap and Wrap” policy. When you go out in the sun, slip on a shirt, slop on sunscreen, slap on a hat and wrap on sunglasses to protect your eyes and the sensitive skin around them.

Exposure to the UV rays of tanning lamps is not safe. Tanning lamps give out UV rays, which can cause long-term skin damage and can contribute to skin cancer. Tanning bed use has been linked with an increased risk of melanoma, especially for people under 30. Most doctors and health organizations recommend not using tanning beds and sun lamps.