Skin cancer is a disease in which rapidly multiplying abnormal cells (cancer cells) are found in the outer layers of the skin.
In 1985 former President Ronald Reagan had a growth called a basal (BAY-zuhl) cell carcinoma * removed from the side of his nose. The president had often been described as looking tanned and healthy, and when the news broke, it raised public awareness of skin cancer and the dangers of overexposure to the sun. Each year, about one million Americans are diagnosed with skin cancer.
The skin is the largest organ of the body. It protects people by keeping water and other fluids inside the body, by helping to regulate body temperature, by manufacturing vitamin D, and by performing a range of other complex functions. The skin is a critically important barrier between people and such foreign invaders as bacteria. The skin is a basic part of physical appearance; it is the surface of the body that people present to the world.
Skin cancer is the most common of all cancers. It accounts for 50 percent of all cases of cancer. Cancers of the skin are divided into two general types: melanoma (mel-a-NO-muh) and nonmelanoma. Non-melanoma cancers are the most common cancers of the skin as well as being the most curable. Melanoma is much less common, but it is far more aggressive and causes 75 percent of all skin cancer deaths.
The two main types of nonmelanoma are basal cell carcinoma and squamous cell carcinoma. These cancers develop in different layers of the skin, but they both appear more commonly on sun-exposed areas of the body. Squamous cell carcinomas grow more quickly than basal cell carcinomas.
Skin cancer begins with damage to the DNA * of the cells in skin. DNA is information people inherit from their parents that tells the cells of the body how to perform all the activities needed for life. DNA is contained in genes * , and each cell has an identical set of genes. Some of these genes carefully control when cells grow, divide, and die. If a gene is damaged, the cell receives the wrong instructions or no instructions at all. When that happens, the cell can begin to grow and divide uncontrollably, forming an unruly cluster that crowds out its neighbors and forms a cancerous growth or tumor. Melanoma is potentially serious because it has the ability to spread to other places in the body. Nonmelanoma, however, tends to stay put and is less likely to spread.
Actinic keratosis (also called solar keratosis, sun spots, or precancerous spots) is an area on the skin that is small and raised, feels scaly or rough, and is located on an area that is exposed to the sun. These areas can develop on the face and scalp, neck, chest, hands, or any place that is often exposed to the sun. The area first appears as a flat patch that is scaly. The scale is white or a yellow crusty substance. In time, the growth may change to appear gray, pink, red, or remain the same color as the surrounding skin. In some cases, the area becomes hard, wart-like, and rough. Often the area is easier to feel than to see.
Not everyone who spends time in the sun develops actinic keratosis, but it develops more easily in people who:
The diagnostic test of choice for actinic keratosis is a skin biopsy (a procedure in which a piece of the area is removed to be analyzed). By examining the cells of the area, the dermatologist (physician who specializes in diseases of the skin) will know whether the area is precancerous or benign and determine the best course of treatment.
Actinic keratoses can be removed or treated in a number of ways:
The physician might also recommend:
If actinic keratosis is treated when initially discovered, the long-term prognosis is very good. Since a percentage of these lesions can become cancerous, it is best to seek medical attention immediately when an abnormality is discovered on the skin.
The best way to avoid the development of actinic keratosis is to avoid exposing unprotected skin to direct sunlight. Ways to do this include:
Certain kinds of risk factors suggest who might be likely to develop cancer. A risk factor is anything that increases a person's chances of getting a disease.
One risk factor is having certain types of moles. Another risk factor is having fair skin. The risk of melanoma is about 20 times higher for light-skinned people than it is for dark-skinned people. However, dark-skinned people can still get melanoma. A person's chances of getting melanoma are greater if one or more close relatives have gotten it. People who have been treated with medicines that suppress the immune system (the body's defenses against infection) have an increased risk of developing melanoma. Exposure to ultraviolet radiation—for example, sunlight, tanning lamps, and tanning booths—also is a risk factor for melanoma. Studies have shown no protective benefit of sunscreens in preventing melanoma.
Most cases of nonmelanoma are caused by unprotected exposure of the area with the cancer to ultraviolet radiation. Most of this radiation comes from sunlight, but it may come from artificial sources. Although children and young adults usually do not get skin cancer, they may get a lot of exposure to the sun that could result in cancer later on. Other risk factors for nonmelanoma include having fair skin and having a weakened immune system as a result of medical treatment for other conditions. In addition, exposure to certain kinds of chemicals increases a person's risk of getting nonmelanoma.
Melanoma may show up as a change in the size, color, texture, or shape of a mole or other darkly pigmented area. Bleeding from a mole that is not the result of a scratch or other injury may also be a warning sign of cancer. Nonmelanoma can be hard to differentiate from normal skin. The most important warning signs are a new growth, a spot or bump that seems to be growing larger (over a few months or a year or two), or a sore that does not heal within three months.
When either melanoma or nonmelanoma is suspected, the doctor will take a sample (biopsy) of the abnormal tissue for examination under the microscope.
Fortunately, most nonmelanomas can be completely cured by a variety of types of surgery depending on the size of the cancer and where it is. If a squamous cell cancer appears to have a high risk of spreading, surgery may sometimes be followed by radiation, which uses high-energy rays to kill cancer cells, or chemotherapy (kee-mo-THER-ah-pee), which uses anticancer drugs that can be injected into a vein in the arm or taken as tablets. For some precancerous conditions, chemotherapy may simply be placed directly on the skin as a cream.
Treatment for melanoma is usually determined by the stage of the cancer. Early stage cancers may be treated with surgery alone. Stage III and stage IV melanomas typically require a combination of treatments, including surgery, chemotherapy, and radiation therapy *
Targeted therapy works by specifically targeting the genetic changes that caused the cancer cell to grow out of control. For example, half of all patients with melanomas have changes or damage to a gene known as BRAF. The damaged BRAF gene codes for making a protein that signals the melanoma cell to multiply quickly. Targeted therapy drugs inhibit the protein and thus shrink tumors and stall their growth. Other melanomas are associated with a change in the gene called C-KIT. There are targeted drugs to tackle these melanomas, too. Some targeted drugs work when chemotherapy has failed, and have demonstrated great promise, even in the treatment of stage IV melanomas.
A popular anti-skin cancer slogan in Australia states: “Slip on a shirt. Slap on a hat. Slop on some sunscreen. Seek shade.” The most important way of lowering the risk of nonmelanoma is to stay out of the sun. This precaution is especially important in the middle of the day, when sunlight is most intense. Because no one wants to stay indoors all day, children and adults can protect their skin by covering it with clothing and by using a sunscreen. The sunscreen should protect users from both UVA and UVB radiation. It should have a skin protection factor (SPF) of at least 15 on areas of the skin that are exposed to the sun. Wide-brimmed hats and wraparound sunglasses with 99 to 100 percent ultraviolet absorption help protect the eyes. Tanning booths should be avoided. Sunscreen, however, does not seem to prevent melanoma.
The most important fact to remember about skin cancer is that most of it is preventable. It is never too late for people to begin to protect their skin. Because a person who has had one skin cancer is at risk for another one, monthly self-examinations should become part of a routine. Cancer is most likely to recur (to come back) in the first five years after treatment. Individuals who love being in the sun must take steps to protect their skin from more exposure. With the exception of staying out of the sun, almost all people with skin cancer can go back to the life they had before they got cancer.
See also Aging • Cancer: Overview • Cataracts • Genetic Diseases: Overview • Hair and Hair Loss • Malignant Melanoma • Radiation Exposure • Skin Conditions: Overview • Tumor
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Riffat, Faruque, Carsten Palme, and Michael Veness. Non-Melanoma Skin Cancer of the Head and Neck. New York: Springer, 2015.
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OncoLink. 3400 Civic Center Blvd., Suite 2338, Philadelphia, PA 19104. Telephone: 215-349-8895. Website: http://www.oncolink.org/index.cfm? (accessed July 10, 2016).
Skin Cancer Foundation. 149 Madison Ave., Suite 901, New York, NY 10016. Telephone: 212-725-5176. Website: http://www.skincancer.org (accessed July 10, 2016).
* carcinoma (kar-sih-NO-muh) is a cancerous tumor that arises in the epithelium (eh-puh-THEElee-um), the sheets of cells that line body surfaces, such as the insides of hollow organs and cavities
* DNA, or deoxyribonucleic acid (dee-OX-see-ry-bo-nyoo-klay-ik A-sid), is the specialized chemical substance that contains the genetic code necessary to build and maintain the structures and functions of living organisms.
* genes (JEENS) are the functional units of heredity that are composed of deoxyribonucleic acid (DNA) and that help determine a person's body structure and physical characteristics. Inherited from a person's parents, genes are segments of chromosomes found in the nuclei of the body's cells.
* ultraviolet light is a wavelength of light beyond visible light. On the spectrum of light, it falls between the violet end of visible light and x-rays.
* radiation therapy is a treatment that uses highenergy radiation from x-rays and other sources to kill cancer cells and shrink cancerous growths