Skin Cancer: Melanoma, Basal Cell, Squamous Cell Carcinoma

As much as we might enjoy spending time in the sun, the fact is it can be damaging to the skin. In fact, in some cases it can lead to skin cancer, the most common form of cancer diagnosed in the United States, according to the American Cancer Society. Genetic mutations can result from damage done to skin cells by UV radiation, and those mutations can sometimes result in out-of-control proliferation of cells, i.e. cancer.

But skin cancer is not a single disease. Rather, it’s a group of diseases related to an unchecked proliferation of certain skin cells. Some types are more common than others, and some are quite rare, but when you hear about skin cancer, you’ll likely be hearing about one of the types outlined below.

— Nonmelanoma skin cancer, which includes:

— Basal cell carcinoma

— Squamous cell carcinoma

— Melanoma

— Less Common Types of Skin Cancer, including:

— Merkel cell skin cancer

— Lymphoma of the skin

— Kaposi sarcoma

— Sebaceous gland carcinoma

— Dermatofibrosarcoma protuberans

— Precancerous Growths

Nonmelanoma Skin Cancer

Dr. Marc Glashofer, a board-certified dermatologist, skin cancer expert, and a fellowship-trained Mohs surgeon practicing in northern New Jersey, says that he breaks skin cancer into two major categories — melanoma and nonmelanoma skin cancer. “The majority of skin cancers diagnosed in the U.S. are nonmelanoma skin cancers,” which are further classified as basal cell carcinoma and squamous cell carcinoma. “There’s about 2 to 3 million basal cell carcinoma diagnoses per year and hundreds of thousands of squamous cell carcinomas diagnosed per year.”

Dr. Pauline Funchain, a medical oncologist who specializes in melanoma at the Cleveland Clinic in Ohio, says nonmelanoma skin cancers don’t tend to metastasize — it’s very rare for those other cancers to spread to other organs,” meaning that these types of skin cancers tend to be less aggressive and can usually be dealt with easily at the intial site of presentation. When a nonmelanoma skin cancer does spread, it’s often related to the patient having a compromised immune system, such as occurs after an organ transplant or with HIV/AIDS. “It’s not that these cancers can’t take lives, but it’s much rarer for them to do that,” than it is for melanoma to become deadly, she says.

[See: What Causes Cancer? 5 Unlikely Claims Explained.]

Basal Cell Carcinoma

Certain cells in the innermost layer of the skin or epidermis, called the basal layer, can sometimes give rise to cancer, particularly when they’ve been damaged by excessive exposure to UV radiation from the sun or a tanning bed. Cancer in these basal cells is called basal cell carcinoma, and it’s the most common form of skin cancer, accounting for about 80 percent of all skin cancers diagnosed in the U.S. The good news is, it tends to be the least aggressive form of skin cancer. “Even though basal cell carcinoma is the most common type of malignancy, when early detection and early intervention is applied, it’s a very survivable thing,” Glashofer says.

Basal cell carcinomas usually begin as raised, flesh-colored bumps that may look like pimples but don’t heal. Other times, they can present as dark or red scaly patches. They’re typically caught early and are often easily treated with a simple surgical excision. “But there are a small percentage of those cancers that can be dangerous. Metastatic basal cell skin cancer is quite rare, but it can happen,” says Dr. Mark Faries, co-director of the melanoma program and head of surgical oncology at The Angeles Clinic and Research Institute, an affiliate of Cedars-Sinai Medical Center in Los Angeles.

Squamous Cell Carcinoma

The other form of nonmelanoma skin cancer, called squamous cell carcinoma, occurs in flat cells in the outer part of the epidermis. This type of skin cancer accounts for nearly 20 percent of all skin cancer diagnoses in the United States.

“Squamous cell carcinomas present often as red, scaly patches,” Glashofer says. “Sometimes they present as rapidly growing nodules or actual lesions that are above the skin surface. They usually are easily treated by similar mechanisms like the basal cells depending on whether it’s on the face, backs of the hands or front of the legs.” Surgical excision using the Mohs technique — in which the excised cells are examined while the patient waits and more tissue can be removed if needed — or scraping the cells away are common ways of treating this type of lesion.

[Read: 9 Ways to Spot Skin Cancer Before It Kills.]

However, there are times when squamous cell carcinomas can metastasize, or spread to other organs, and it can be deadly. “This is more likely to happen when a squamous cell carcinoma is over two centimeters in size or when it’s too deep,” Glashofer says. Tumors that have burrowed deeper in the skin have access to more blood vessels, which can aid in transporting cancerous cells to other parts of the body where they can set up shop in other organs. “The lip, the ear or even the backs of the hands are areas that are more prone to have regional or distant metastasis, just based on the fact that there’s more blood vessels in those areas.” No matter where they occur, Glashofer says, “squamous cells are legitimate lesions that need to be treated with respect.”


Our skin and eyes contain thousands of cells called melanocytes. These cells produce and contain melanin, the pigment that gives our skin and eyes their color. When an unchecked overgrowth of these cells occurs, that’s called melanoma, and it’s an aggressive form of skin cancer. Although melanoma is relatively rare — accounting for only about 1 percent of all skin cancer diagnoses — it causes the majority of skin cancer–related deaths. The American Academy of Dermatology reports that in 2019, 192,310 new cases of melanoma are expected to be diagnosed and an estimated “7,230 deaths will be attributed to melanoma — 4,740 men and 2,490 women.” Melanoma rates doubled from 1982 to 2011 and are continuing to rise.

The National Cancer Institute reports that “often the first sign of melanoma is a change in the shape, color, size or feel of an existing mole. However, melanoma may also appear as a new mole.” This is why many doctors tell patients to check their skin regularly and use the ABCDE guide to help them determine whether a mole or spot needs further evaluation:

Asymmetry. An asymmetrical mole or spot should be evaluated.

Border. If your mole or spot has a jagged, notched or irregular border, that should be checked out.

Color. Uneven color could be a sign of skin cancer.

Diameter. Bigger moles and spots are of greater concern than smaller ones and should be evaluated.

Evolving. If your questionable mole or spot has changed recently, talk to your doctor.

As with nonmelanoma skin cancer, exposure to UV radiation from the sun or tanning beds can elevate your risk of developing melanoma, but it seems to be less of a factor than with basal cell and squamous cell carcinomas. “Some people may get (melanoma) on the buttocks or the bottoms of feet that never see the sun, but they get these pigmented lesions. Or it may develop in an area where you can’t see it. Those are areas that have worse prognoses because they’ve been lingering and they’re there for a much longer period of time,” Glashofer says.

While melanoma can be deadly, recent innovations in immunotherapy and targeted treatments are improving outcomes and extending life expectancy for people with metastatic melanoma. “Melanoma used to be the dark spot, the depressing area of oncology because there wasn’t a whole lot of useful stuff going on. Chemotherapy didn’t work very well and was kind of weak,” Faries says. “But just in the last 10 years, really, there has been a revolution. Melanoma now leads the rest of oncology in terms of progress and breakthrough, and it’s a rapidly moving field. Anyone who’s facing a diagnosis should seek up-to-date information about what to do. Look for clinical trials and people with experience in treating it,” he says.

[Read: Ways to Prevent Skin Cancer.]

Less Common Types of Skin Cancer

Nearly all skin cancers diagnosed in the U.S. are nonmelanomas or melanoma. But there are a few other very rare types of skin cancer that can develop. Combined, these types of skin cancer make up less than 1 percent of all skin cancers diagnosed in the U.S. today.

Merkel cell skin cancer. This rare type of skin cancer starts when so-called Merkel cells grow out of control. These cells are found at the base of the top layer of skin. They’re called neuroendocrine cells because they are close to nerve endings and have some hormone-making characteristics. While this is a very rare type of skin cancer, it’s very aggressive. Merkel cell skin cancer can start anywhere on the body, but it tends to be found more often on areas of skin that receive lots of sun exposure. These lesions may appear as firm pink, red or purple lumps on the skin. They can metastasize to the brain, bones, lungs or liver.

Lymphoma of the skin. Lymphoma is a form of cancer that starts in the white blood cells, also called lymphocytes. This type of cancer is usually described as Hodgkin lymphoma or non-Hodgkin lymphoma. Lymphoma can start in any part of the body, but when it begins only in the skin, the cancer is described as lymphoma of the skin. It usually shows up as an extremely itchy, patchy rash that looks like sunburn. The skin may be thickened, and lymphoma cells, called Sezary cells, may be found in the blood and lymph nodes as well. Lymphomas of the skin may also look like pimply lesions or larger lumps or bumps under the skin.

Kaposi sarcoma. Another rare form of skin cancer, Kaposi sarcoma develops in cells that line lymph or blood vessels. It’s caused by the herpes virus and it usually appears as a purple, red or brown blotch or tumor on the skin or inside the mouth. KS can also develop in other locations such as the lungs or digestive tract, and it can be serious if the lesions emerge in the lungs, liver or digestive tract. They occur more commonly in people with an immune deficiency, such as occurs with HIV or AIDS, or in immune-suppressed patients such as those who’ve had an organ transplant.

Sebaceous gland carcinoma. This very rare and aggressive cancer starts in the oil glands in the skin, and usually impacts women over the age of 70. Most of these cancers are found near the eye, but they can also grow on the head, neck, torso or in the genital region.

Dermatofibrosarcoma protuberans. DFSP is a very rare form of soft tissue sarcoma that starts in deep layers of skin. The NIH reports that DFSP tumors often start as small, firm patches of skin that are purplish, reddish or flesh-colored. It’s often found in the chest or shoulder region. It’s a slow-growing form of cancer that usually doesn’t spread but is likely to recur after surgical excision.

Precancerous growths. In addition to cancerous lesions, some people also develop precancerous lesions that may need to be removed before they become cancerous and cause bigger problems. The Skin Cancer Foundation reports that actinic keratosis is the most common precancer, affecting more than 58 million Americans. Specifically, AK is a type of precancerous growth that tends to develop on skin damaged by exposure to UV radiation. These lesions may develop into squamous cell carcinoma if not treated so are typically removed. They often appear as a crusty, scaly growth on skin that’s often exposed to sunlight. Keratoacanthoma is another type of benign tumor that looks like a small dome or crater in the skin. They tend to be fast growing and more common among older, light-skinned people. They often develop at the site of a previous injury or trauma, the American Osteopathic College of Dermatology reports. KA tumors tend to go away on their own over the course of about a year, but it’s often difficult to distinguish them from squamous cell carcinomas and it may be best to have the lesion removed to be sure.

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