Skin Cancer – Harvard Health

What is skin cancer?

Skin cancer occurs when skin cells are damaged by ultraviolet (UV) rays from repeated sun exposure and sunburns. Exposure to UV radiation from tanning beds and sunlamps can also increase skin cancer risk.

The two most common skin cancers are basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). They are slow-growing and seldom spread to other parts of the body. Both can be treated, but they can be disfiguring.

Melanoma is the most dangerous skin cancer. Though less common—accounting for about 1% of skin cancers—melanoma is responsible for the majority of skin cancer deaths. Melanoma is fast-growing and more likely to spread than BCC and SCC.

Skin cancer develops primarily on areas of sun-exposed skin, such as the scalp, face, ears, neck, lips, chest, arms, hands, and legs. But it also can form in other areas like the palms, beneath the fingernails and toenails, and genitals.

Besides overexposure to UV rays, other factors that increase one’s risk for skin cancer include having:

  • fair skin
  • blond or red hair
  • blue, green, or gray eyes
  • skin that burns easily
  • a family history of skin cancer
  • a tendency to develop moles or abnormal appearing or large moles
  • previous bad sunburns
  • older age

The best way to lower your risk for skin cancer is to protect your skin from UV light. Use sunscreen on exposed skin whenever outside and wear protective clothing, including wrap-around sunglasses and a wide-brim hat.

What are the symptoms of skin cancer?

Skin cancers commonly appear on the most sun-exposed areas of the body, like the face, ears, neck, lips, and backs of the hands. They can also develop in scars, skin sores, or rashes elsewhere on the body. Here is what common skin cancers look like.

Basal cell carcinoma (BCC). BCCs usually appear as tiny, painless bumps with a pink, pearly surface. As it slowly grows, the center of the bump may become sore and develop into a crater that bleeds, crusts, or forms a scab. Although it is commonly located on the face, basal cell cancer can develop on the ears, back, and neck.

Squamous cell carcinoma  (SCC). SCCs usually begin as a small, red, painless lump or skin patch that slowly grows and may develop into a non-healing sore. It usually occurs on the head, ears, and hands.

Melanoma. Melanoma is usually visible as a single dark skin spot. It may appear anywhere on the body, but it most commonly develops on the back, chest, and legs. Most of the time, melanoma develops on normal-looking skin, but it can grow out of an existing mole. Following the ABCDE guideline is a good way to recognize the warning signs for possible melanoma.

  • A: Asymmetry: One half of a mole or spot does not match the other.
  • B: Border irregularity: The edges are ragged, notched, or blurred.
  • C: Color: The pigmentation is not uniform; the coloring may include shades of tan, brown, or black; dashes of red, white, or blue can add to the mottled appearance.
  • D: Diameter: A mole or spot is greater than ¼ inch in diameter or about the width of a pencil eraser. However, melanomas can be smaller.
  • E: Evolving: A mole or spot looks different from others and/or changes size, shape, or color; or begins to itch, hurt, or bleed. A mole that bleeds, feels numb, or has a crusty surface also may indicate a melanoma.

Types of skin cancer

The most common types of skin cancer are basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). Less common are melanoma and the even more rare Merkel cell carcinoma, the two leading causes of death from skin cancer.

Most skin cancers start in the top layer of the skin, called the epidermis. The main difference between skin cancers  is the type of cell from which each originates.

Basal cell carcinoma (BCC). BCC is the most common type of skin cancer, accounting for approximately 80% of cases. It starts in basal cells located deep in the epidermis. BCCs tend to grow slowly, and it’s rare for a BCC to spread to other parts of the body. But if left untreated, BCCs can grow into nearby areas, deep into the skin, and destroy bone and tissue. If not fully eradicated during treatment, BCCs can return to the same place. People with BCCs are also more likely to get new ones elsewhere.

Squamous cell carcinoma (SCC). About 20% of skin cancers are SCC. They begin in the squamous cells in the middle and outer parts of the epidermis. SCC sometimes develop from a precancerous skin growth called an actinic keratosis, a rough, scaly patch on the skin that usually affects older adults after years of sun exposure. SCCs also are slow-growing, although they are more likely than BCCs to grow into deeper layers of the skin and spread to other parts of the body.

Melanoma. This type of skin cancer forms from melanocytes, skin cells in the bottom layer of the epidermis. Melanoma only makes up about 1% of skin cancers but it’s the deadliest because affected melanocytes can multiply and spread quickly.

Merkel cell carcinoma. This skin cancer is 40 times more rare than melanoma and forms from Merkel cells found in the layer of basal cells. It also tends to grow and spread quickly and is the second most common cause of skin cancer death after melanoma. 

What is melanoma

Melanoma (also known as malignant melanoma) is the deadliest form of skin cancer. It occurs when melanocytes (the cells that give skin its color) begin to reproduce uncontrollably. Melanoma can grow quickly and spread to other parts of the body.

Melanoma is usually visible as a single dark skin spot, often larger than 6 millimeters (mm) in diameter (about the size of a pencil eraser) but sometimes smaller. Melanoma can form from an existing mole or develop on normal-looking skin. Certain features of moles can raise the risk of melanoma, such as: 

  • A new mole appearing after age 30  
  • A new mole at any age if it is in an area rarely exposed to the sun  
  • A change in an existing mole  
  • One or more atypical moles—moles that resemble a fried egg, that are darker than others, or have an irregular shape.  
  • 20 or more moles on the body larger than 2 mm across  
  • Five or more moles each larger than 5 mm across

The most common sites for melanoma are the face (especially in older people), upper trunk (primarily in men), and legs (mostly in women). Melanoma can also appear on other parts of the body, such as under fingernails or toenails, the genitals, and inside the eye.

Melanoma is often easy to spot early. Regularly check your skin to look for new moles and for changes in existing ones.

People at increased risk for melanoma need regular checkups from their doctor or dermatologist. Because some melanomas can arise from existing moles, a doctor or dermatologist may remove atypical moles as they may be more likely to become cancerous.

Determining whether a mole or other spot is melanoma usually involves removing a small piece and some of the surrounding tissue and examining it for cancer.

There are five stages of melanoma—zero to four—with each stage defined by the melanoma’s thickness, how deep it has penetrated the skin, and whether it has spread. The higher the number, the more extensive the disease and, generally, the worse the prognosis.

Tumors on the skin’s surface can usually be cured, but deeper cancers are more difficult and sometimes impossible to treat.

If treatment begins when the tumor is less than 0.75 mm deep, the chance of a cure is excellent. More than 95% of people with small melanomas are cancer-free as long as eight years later. However, for deeper melanomas, the survival rate is poor.

How can you prevent skin cancer?

To help prevent skin cancer, follow standard sun protection guidelines. For example:

Sunscreen. The mantra for sunscreen is to use it early and often. Apply sunscreen 15 to 20 minutes before heading outside then reapply every two hours. Use at least two tablespoons to cover exposed areas of the face and body, with a nickel-sized dollop to the face alone. And don’t forget the ears, the tops of the feet, and the backs of the legs.

When choosing a sunscreen, focus on broad-spectrum coverage, SPF number, and water resistance.

Broad-spectrum coverage. This means the sunscreen protects against UVB sun rays—the leading cause of sunburns—and UVA, which penetrates deeper into the skin and contributes to skin aging and wrinkles. Both types of UV rays can damage DNA, raising the risk of skin cancer. Other terms you might see on labels that mean the same thing are “multi-spectrum” or “UVA/UVB protection.”

SPF. This stands for sun protection factor. The higher the SPF number, the greater the protection. For instance, SPF 30 blocks 97% of the UVB rays, and SPF 50 blocks 98%. Anything higher than 70 SPF does not provide much extra protection. Stick with sunscreen with a 30 to 50 SPF.

Water resistance. No sunscreen is waterproof, but water-resistant sunscreen withstands water and sweat for a limited time. It’s best to reapply sunscreen after getting out of the water or if you’ve been sweating a lot.

Attire. Wear a hat with at least a four-inch brim all around and sunglasses that block sunlight from the sides. As for clothing, opt for synthetic fibers, such as polyester, Lycra, nylon, and acrylic. These have elastic threads that pull the fibers close together, which reduces the spaces between them and thus blocks more of the sun’s UV rays. Color matters, too.  Darker colors are better at protecting the skin against  UV rays than lighter colors.

Some clothing brands offer specially designed sun protection clothing, which is marked with a UPF (ultraviolet protection factor) label and number. The number indicates what fraction of the sun’s UV rays can penetrate the fabric and reach your skin. For example, a shirt with a UPF of 50 allows only one-fiftieth of the sun’s rays through, according to the Skin Cancer Foundation.

Time. Avoid the sun from 10 a.m. to 2 p.m., when ultraviolet (UV) radiation exposure is at its peak.

Check your skin. Get a professional skin check from a dermatologist every one to two years. Those with previous skin cancer or strong family history should be checked more often. Also, keep an eye on your skin. Routinely check your body in the mirror for unusual spots, growths, or suspicious moles. Ask your spouse, partner, or a family member to look at your back and other areas you can’t see, like the scalp and the backs of the thighs and ears. Consult your doctor or dermatologist if you notice any suspicious spots, growths, or moles that get larger, become darker, or change shape.

How is skin cancer treated?

Many skin cancers are treatable if caught early. Your dermatologist may recommend various treatments depending on the type of skin cancer, its size and location, how far it’s spread, and whether a treated skin cancer has returned.

Melanoma. Surgery is the initial treatment for melanoma that appears in just one spot. The doctor removes the visible tumor along with 0.5 to 2 centimeters of healthy skin around the tumor, depending on its size.

In some cases, the doctor may perform Mohs surgery, a specialized procedure in which the tumor is shaved away one thin layer at a time and examined under the microscope. If any cancer cells remain, another layer of tissue is removed, and the process is repeated until no cancer cells appear in the removed sample. This technique helps the doctor remove as little healthy skin as possible.  

If the melanoma is more than 1 millimeter deep, your doctor must determine if it has spread to nearby lymph nodes. If cancer is found, most often all of the lymph nodes in the area will be removed. However, it has not been absolutely proven that removing all lymph nodes improves the chances of survival. When a cancer has spread to only one or two other sites, surgical removal can improve survival.

Additional therapies can often help people with thicker tumors that have grown deep into the skin, spread to other areas of the body, or both. Most often, patients are treated with immunotherapy and/or drugs designed to block major pathways that allow cancers to grow. Radiation therapy and chemotherapy are less effective but can be used when other treatments stop working.

Basal cell carcinoma and squamous cell carcinoma. BCC and SCC share similar treatments. These include:

  • cutting away the cancer and a small amount of healthy tissue around it. A skin graft may be necessary if a large area of skin is removed.
  • scraping away the cancer with a surgical tool then using an electric probe to kill any remaining cancer cells.
  • freezing cancer cells with liquid nitrogen.
  • destroying the tumor with radiation.
  • Mohs surgery.
  • applying drugs directly to the skin or injecting them into the tumor.
  • using a narrow laser beam to destroy the cancer.

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