Skin cancer — the abnormal growth of skin cells — most often develops on skin exposed to the sun. But this common form of cancer can also occur on areas of your skin not ordinarily exposed to sunlight. There are three major types of skin cancer — basal cell carcinoma, squamous cell carcinoma and melanoma. You can reduce your risk of skin cancer by limiting or avoiding exposure to ultraviolet (UV) radiation. Checking your skin for suspicious changes can help detect skin cancer at its earliest stages. Early detection of skin cancer gives you the greatest chance for successful skin cancer treatment.
Causes of Skin Cancer
Skin cancer occurs when errors (mutations) form the in the DNA of healthy skin cells. The mutations cause the cells to grow out of control and form a mass of cancer cells.
Cells involved in skin cancer
Skin cancer begins in your skin's top layer — the epidermis. The epidermis is a thin layer that provides a protective cover of skin cells that your body continually sheds. The epidermis contains three main types of cells:
Squamous cells lie just below the outer surface and function as the skin's inner lining.
Basal cells, which produce new skin cells, sit beneath the squamous cells.
Melanocytes — which produce melanin, the pigment that gives skin its normal color — are located in the lower part of your epidermis. Melanocytes produce more melanin when you're in the sun to help protect the deeper layers of your skin. Extra melanin produces the darker color of tanned skin.
Where your skin cancer begins determines its type and your treatment options.
Ultraviolet light and other potential causes
Much of the damage to DNA in skin cells results from ultraviolet (UV) radiation found in sunlight and in commercial tanning lamps and tanning beds. But sun exposure doesn't explain skin cancers that develop on skin not ordinarily exposed to sunlight. This indicates that other factors may contribute to your risk of skin cancer, such as being exposed to toxic substances or having a condition that weakens your immune system.
Signs & Symptoms of Skin Cancer
Where skin cancer develops
Skin cancer develops primarily on areas of sun-exposed skin, including the scalp, face, lips, ears, neck, chest, arms and hands, and on the legs in women. But it can also form on areas that rarely see the light of day — your palms, beneath your fingernails, the spaces between your toes or under your toenails, and your genital area. Skin cancer affects people of all skin tones, including those with darker complexions. When melanoma occurs in those with dark skin tones, it's more likely to occur in areas not normally considered to be sun-exposed.
Basal cell carcinoma signs and symptoms
Basal cell carcinoma usually occurs in sun-exposed areas of your body, such as your face, ears or scalp. Basal cell carcinoma may appear as:
A pearly or waxy bump
A flat, flesh-colored or brown scar-like lesion
Squamous cell carcinoma signs and symptoms
Most often, squamous cell carcinoma occurs on sun-exposed areas of your body, such as your face, lips, ears and hands. Squamous cell carcinoma may appear as:
A firm, red nodule
A flat lesion with a scaly, crusted surface
Melanoma signs and symptoms
Melanoma can develop anywhere on your body, in otherwise normal skin or in an existing mole that becomes cancerous. Melanoma most often appears on the trunk, head or neck of affected men. In women, this type of cancer most often develops on the lower legs. In both men and women, melanoma can occur on skin that hasn't been exposed to the sun. Melanoma can affect people of any skin tone. In people with darker skin tones, melanoma tends to occur on the palms or soles, or under the fingernails or toenails.
Melanoma signs include:
A large brownish spot with darker speckles
A mole that changes in color, size or feel or that bleeds
A small lesion with an irregular border and portions that appear red, white, blue or blue-black
Dark lesions on your palms, soles, fingertips or toes, or on mucous membranes lining your mouth, nose, vagina or anus
Signs and symptoms of less common skin cancers
Other, less common types of skin cancer include:
Kaposi sarcoma. This rare form of skin cancer develops in the skin's blood vessels and causes red or purple patches on the skin or mucous membranes. Kaposi sarcoma mainly occurs in people with weakened immune systems, such as people with AIDS, and in people taking medications that suppress their natural immunity, such as people who've undergone organ transplants. Kaposi sarcoma can also occur in older adults of Mediterranean heritage.
Merkel cell carcinoma. Merkel cell carcinoma causes firm, shiny nodules that occur on or just beneath the skin and in hair follicles. Merkel cell carcinoma is usually found on sun-exposed areas on the head, neck, arms and legs.
Sebaceous gland carcinoma. This uncommon and aggressive cancer originates in the oil glands in the skin. Sebaceous gland carcinomas — which usually appear as hard, painless nodules — can develop anywhere, but most occur on the eyelid, where they're frequently mistaken for other eyelid problems.
Diagnosis of Skin Cancer
Diagnosing skin cancer
To diagnose skin cancer, your doctor may:
Examine your skin. Your doctor may look at your skin to determine whether your skin changes are likely to be skin cancer. Further testing may be needed to confirm that diagnosis.
Remove a sample of suspicious skin for testing (skin biopsy). Your doctor may remove a small sample of suspicious-looking skin for laboratory testing. A biopsy can determine whether you have skin cancer and, if so, what type of skin cancer you have.
Determining the extent of the skin cancer
If your doctor determines you have skin cancer, he or she may recommend additional tests to determine the extent, or stage, of the skin cancer. Because superficial skin cancers such as basal or squamous cell carcinoma rarely spread, a biopsy often is the only test needed to determine the cancer stage. But if you have a large growth or one that's existed for some time, your doctor may recommend further tests to determine the extent of the cancer.
Skin cancer is generally divided into two stages:
Local. In this stage, cancer affects only the skin.
Metastatic. At this point, cancer has spread beyond the skin.
The skin cancer's stage helps determine which treatment options will be most effective.
Treatments of Skin Cancer
Treatment for skin cancer and the precancerous skin lesions known as actinic keratoses varies, depending on the size, type, depth and location of the lesions. Small skin cancers limited to the surface of the skin may not require treatment beyond an initial skin biopsy that removes the entire growth.
If additional treatment is needed, options may include:
Freezing. Your doctor may destroy actinic keratoses and some small, early skin cancers by freezing them with liquid nitrogen (cryosurgery). The dead tissue sloughs off when it thaws.
Excisional surgery. This type of treatment may be appropriate for any type of skin cancer. Your doctor cuts out (excises) the cancerous tissue and a surrounding margin of healthy skin. A wide excision — removing extra normal skin around the tumor — may be recommended in some cases.
Laser therapy. A precise, intense beam of light vaporizes growths, generally with little damage to surrounding tissue and with minimal bleeding, swelling and scarring. A doctor may use this therapy to treat superficial skin cancers.
Mohs surgery. This procedure is for larger, recurring or difficult-to-treat skin cancers, which may include both basal and squamous cell carcinomas. Your doctor removes the skin growth layer by layer, examining each layer under the microscope, until no abnormal cells remain. This procedure allows cancerous cells to be removed without taking an excessive amount of surrounding healthy skin.
Curettage and electrodesiccation. After removing most of a growth, your doctor scrapes away layers of cancer cells using a circular blade (curet). An electric needle destroys any remaining cancer cells. This simple, quick procedure is common in treating small or thin basal cell cancers.
Radiation therapy. Radiation may be used in situations when surgery isn't an option.
Chemotherapy. In chemotherapy, drugs are used to kill cancer cells. For cancers limited to the top layer of skin, creams or lotions containing anti-cancer agents may be applied directly to the skin. Topical drugs can cause severe inflammation and leave scars. Systemic chemotherapy can be used to treat skin cancers that have spread to other parts of the body.
Photodynamic therapy (PDT). This treatment destroys skin cancer cells with a combination of laser light and drugs that makes cancer cells sensitive to light. PDT makes your skin sensitive to light, so you will need to avoid direct sunlight for at least six weeks after treatment.
Biological therapy. Biological treatments stimulate your immune system in order to kill cancer cells. Biological therapy medications used to treat certain skin cancer include interferon and interleukin-2.
Prevention of Skin Cancer
Most skin cancers are preventable. To protect yourself, follow these skin cancer prevention tips:
Avoid the sun during the middle of the day. For many people in North America, the sun's rays are strongest between about 10 a.m. and 4 p.m. Schedule outdoor activities for other times of the day, even in winter or when the sky is cloudy. You absorb UV radiation year-round, and clouds offer little protection from damaging rays. Remember, sunburns and suntans cause skin damage that can increase your risk of developing skin cancer. Sun exposure accumulated over time also may cause skin cancer.
Wear sunscreen year-round. Sunscreens don't filter out all harmful UV radiation, especially the radiation that can lead to melanoma. But they play a major role in an overall sun protection program. Choose a broad-spectrum sunscreen that has a sun protection factor (SPF) of at least 15. Use a generous amount of sunscreen on all exposed skin, including your lips, the tips of your ears, and the backs of your hands and neck.
Wear protective clothing. Sunscreens don't provide complete protection from UV rays. So cover your skin with dark, tightly woven clothing that covers your arms and legs, and a broad-brimmed hat, which provides more protection than a baseball cap or visor does. Some companies also sell photoprotective clothing. A dermatologist can recommend an appropriate brand. Don't forget sunglasses. Look for those that block both types of UV radiation — UVA and UVB rays.
Avoid tanning beds. Tanning beds emit UV rays and can increase your risk of skin cancer.
Be aware of sun-sensitizing medications. Some common prescription and over-the-counter drugs — including antibiotics; certain cholesterol, high blood pressure and diabetes medications; and nonsteroidal anti-inflammatory drugs such as ibuprofen (Advil, Motrin, others) — can make your skin more sensitive to sunlight. Ask your doctor or pharmacist about the side effects of any medications you take. If they increase your sensitivity to sunlight, take extra precautions to stay out of the sun in order to protect your skin.
Check your skin regularly and report changes to your doctor. Examine your skin often for new skin growths or changes in existing moles, freckles, bumps and birthmarks. With the help of mirrors, check your face, neck, ears and scalp. Examine your chest and trunk, and the tops and undersides of your arms and hands. Examine both the front and back of your legs, and your feet, including the soles and the spaces between your toes. Also check your genital area and between your buttocks.
When to seek Medical Advice
Make an appointment with your doctor if you notice any changes to your skin that worry you. Not all skin changes are caused by skin cancer. Your doctor will investigate your skin changes to determine a cause.