Skin cancer is a malignant growth of the external surface or epithelial layer of the skin.
Skin cancer is the growth of abnormal cells capable of invading and destroying other associated skin cells. Skin cancer is often subdivided into either melanoma or non-melanoma. Melanoma is a dark-pigmented, usually malignant, tumor arising from a skin cell capable of making the pigment melanin (a melanocyte). Melanoma can spread throughout the body via the bloodstream or lymphatic system. Non-melanoma skin cancer most often originates from the external skin surface as a squamous cell carcinoma or a basal cell carcinoma.
The cells of a cancerous growth originate from a single cell that reproduces uncontrollably, resulting in the formation of a tumor. Exposure to sunlight is documented as the main cause of almost 800,000 cases of skin cancer diagnosed each year in the United States. The incidence increases for those living where direct sunshine is plentiful, such as in regions near the equator.
Basal cell carcinoma affects the skin's basal layer and has the potential to grow progressively larger in size, although it rarely spreads to distant areas (metastasizes). Basal cell carcinoma accounts for 80% of skin cancers (excluding melanoma), whereas squamous cell cancer makes up about 20%. Squamous cell carcinoma is a malignant growth of the external surface of the skin. Squamous cell cancers metastasize at a rate of 2–6%, with up to 10% of lesions affecting the ear and lip.
Causes & symptoms
Cumulative sun exposure is considered a significant risk factor for non-melanoma skin cancer. High incidence has been noted in individuals with freckles, light hair, and light complexion; in individuals with darker skin, the palms, soles, mucous membranes, and other areas of light pigmentation are the most common sites for melanomas.
Pre-existing moles can change into melanomas, and should be observed for any particular change in appearance, specifically the classic ABCD appearance, in which asymmetrical borders, colors, and diameter are observed. Lesions typically are circular with irregular or asymmetrical borders. Melanomas typically have a combination of colors, including tan, brown, black, or gray; there may also be a dull pink or rose pigmentation within a small area of the lesion. The diameter of a malignant melanoma is typically greater than that of a pencil eraser.
There is evidence suggesting that early intense sun exposure causing blistering sunburn in childhood may also play an important role in the cause of non-melanoma skin cancer. Basal cell carcinoma most frequently affects the skin of the face, with the next most
common sites being the ears, the backs of the hands, the shoulders, and the arms. It is prevalent in both sexes, and most commonly occurs in people over the age of 40.
Basal cell carcinoma usually appears as a small skin lesion that persists for at least three weeks. This form of non-melanoma cancer looks flat and waxy, with the edges of the lesion translucent and rounded. The edges also contain small fresh blood vessels. An ulcer found in the center gives the lesion a dimpled appearance. Basal cell carcinoma lesions vary from 4–6 mm in size, but can slowly grow larger if left untreated.
Squamous cell carcinoma also involves skin exposed to the sun, such as the face, ears, hands, or arms. This form of non-melanoma cancer also is most common among people over the age of 40. Squamous cell carcinoma presents itself as a small, scaling, raised bump on the skin with a crusting ulcer in the center, but without itching .
Basal cell and squamous cell carcinomas can grow more easily when people have a suppressed immune system because they are taking immunosuppressive drugs or are exposed to radiation. Some people must take immunosuppressive drugs to prevent the rejection of a transplanted organ or because they have a disease in which the immune system attacks the body's own tissues, referred to as autoimmune illnesses; others may need radiation therapy to treat another form of cancer. Because of the increased risk of skin cancer, all people taking these immunosuppressive drugs or receiving radiation treatments should undergo complete skin examination at regular intervals. If proper treatment is delayed and the tumor continues to grow, the tumor cells can spread, or metastasize, to other muscles, bones, nerves, and possibly to the brain.
About 1–2% of all skin cancers develop within burn scars; squamous cell carcinomas account for about 95% of these cancers, with 3% being basal cell carcinomas and the remainder malignant melanomas.
To diagnose skin cancer, doctors must carefully examine the lesion and ask the patient how long it has been there, whether it itches or bleeds, and other questions about the patient's medical history. If skin cancer cannot be ruled out, a biopsy is performed, in which a sample of the tissue is removed and examined under a microscope. A definitive diagnosis of melanoma, squamous, or basal cell cancer can only be made with microscopic examination of the tumor cells. Once skin cancer has been diagnosed, the stage of the disease's development is determined. The information from the biopsy and staging allows the physician and patient to plan for treatment and possible surgical intervention.
Alternative medicine aims to prevent rather than treat skin cancer. Vitamins have been shown to prevent sunburn and possibly skin cancer. Some dermatologists have suggested that taking antioxidant vitamins E and C by mouth may help prevent sunburn. In one particular study, men and women took these vitamins for eight days prior to being exposed to ultraviolet light. The researchers found that those who consumed vitamins required about 20% more ultraviolet light to induce sunburn than did people who did not take vitamins. This is the first study that indicates the oral use of vitamins E and C increases resistance to sunburn. These antioxidants are thought to reduce the risk of skin cancer and are thought to provide protection from the sun even if taken in lower doses. Other antioxidant nutrients, including beta carotene, selenium, zinc , and the bioflavonoid quercetin, may also help prevent skin cancer, as may such antioxidant herbs as bilberry (Vaccinium myrtillus ), hawthorn (Crataegus laevigata ), turmeric (Curcuma longa ), and ginkgo (Ginkgo biloba ).
A team of researchers at Duke University reported in 2003 that topical application of a combination of 15% vitamin C and 1% vitamin E over a four-day period offered significant protection against sunburn. The researchers suggest that this combination may protect skin against aging caused by sunlight as well.
Another antioxidant that appears to counter the effects of severe sun exposure is superoxide dismutase, or SOD. SOD must be given in injectable form, however, because it is destroyed in the digestive tract.
As of 2003, researchers are also looking at botanical compounds that could be added to skin care products applied externally to lower the risk of skin cancer. Several botanical compounds have been tested on animals and found to be effective in preventing skin cancer, but further research needs to be done in human subjects.
A wide surgical removal of the melanoma and surrounding tissue is usually necessary. Surgery may also include removal of affected lymph nodes, usually followed by skin grafting, which is a process in which a piece of skin that is taken from a donor area replaces the skin removed.
Since the early 1990s, some melanomas have been treated with chemotherapy (usually carmustine or lomustine); other biological therapies are also being used as of 2003.
A variety of treatment options are available for those diagnosed with non-melanoma skin cancer. Some carcinomas can be removed by cryosurgery, the process of freezing with liquid nitrogen. Uncomplicated and previously untreated basal cell carcinoma of the torso and arms is often treated with curettage and electrodesiccation, which is the scraping of the lesion and the destruction of any remaining malignant cells with an electrical current. Moh's surgery, or removal of a lesion layer by layer down to normal margins, is an effective treatment for both basal and squamous cell carcinoma. Radiation therapy is best reserved for older, debilitated patients, or those whose tumors are considered inoperable. Laser therapy is sometimes useful in specific cases; however, this form of treatment is not widely used to treat skin cancer.
Both squamous and basal cell carcinoma are curable with appropriate treatment. Early detection remains critical for a positive prognosis.
Avoiding exposure to the sun reduces the incidence of non-melanoma skin cancer. Sunscreen with a sun-protective factor (SPF) of 15 or higher is helpful in prevention, along with a hat and clothing to shield the skin from sun damage. Individuals who are physically active while exposed to sunlight should consider using waterproof sunscreen, or reapply it. There are many different brands of sunscreen for those with certain skin allergies . People should examine their skin monthly for unusual lesions, especially if previous skin cancers have been experienced.
Advances in photographic technique have now made it easier to track the development of moles with the help of whole-body photographs. A growing number of hospitals are offering these photographs as part of outpatient mole-monitoring services.
Chandrasoma, Parakrama, and Clive R. Taylor. Concise Pathology. East Norwalk, CT: Appleton and Lange, 1991.
Copstead, Lee-Ellen C. "Alterations in the Integument." In Perspectives on Pathophysiology. Philadelphia: W.B. Saunders, 1994.
"Dermatologic Disorders: Malignant Tumors." Section 10, Chapter 126 in The Merck Manual of Diagnosis and Therapy, edited by Mark H. Beers, MD, and Robert Berkow, MD. Whitehouse Station, NJ: Merck Research Laboratories, 2002.
"Dermatologic Disorders: Reactions to Sunlight." Section 10, Chapter 119 in The Merck Manual of Diagnosis and Therapy, edited by Mark H. Beers, MD, and Robert Berkow, MD. Whitehouse Station, NJ: Merck Research Laboratories, 2002.
Pelletier, Kenneth R., MD. The Best Alternative Medicine, Part I: Food for Thought. New York: Simon & Schuster, 2002.
Bray, C. "The Development of an Improved Method of Photography for Mole-Monitoring at the University Hospital of North Durham." Journal of Audiovisual Media in Medicine 26 (June 2003): 60–66.
Brown, C. K., and J. M. Kirkwood. "Medical Management of Melanoma." Surgical Clinics of North America 83 (April 2003): 283–322.
F'guyer, S., F. Afaq, and H. Mukhtar. "Photochemoprevention of Skin Cancer by Botanical Agents." Photodermatology, Photoimmunology and Photomedicine 19 (April 2003): 56–72.
Jellouli-Elloumi, A., L. Kochbati, S. Dhraief, et al. "Cancers Arising from Burn Scars: 62 Cases." [in French] Annales de dermatologie et de venereologie 130 (April 2003): 413–416.
American Academy of Dermatology. 930 N. Meacham Road, Schaumburg, IL 60173. (847) 330–0230 or (888) 462–DERM (227–3376).
American Cancer Society. 1599 Clifton Road NE, Atlanta, GA 30329. (800) ACS-2345.
Centers for Disease Control and Prevention (CDC) Cancer Prevention and Control Program. 4770 Buford Highway, NE, MS K64, Atlanta, GA 30341. (888) 842-6355. <http://www.cdc.gov/cancer/comments.htm>.
National Cancer Institute (NCI). NCI Public Inquiries Office, Suite 3036A, 6116 Executive Boulevard, MSC8332, Bethesda, MD 20892-8322. (800) 4-CANCER or (800) 332-8615 (TTY). <http://www.nci.nih.gov>.
Rebecca J. Frey, PhD
Skin cancer refers to abnormal cells of the skin that grow uncontrollably. If untreated these cells can grow deeper into the skin and invade other tissues. There are three main types of skin cancer: basal cell carcinoma, squamous cell carcinoma and melanoma. All three types are related to excessive sun exposure.
Cancer which is also called a neoplasm, carcinoma or malignancy is a group of diseases where abnormal cells continuously grow out of control. These cells can spread to other organs and if not controlled can result in death . Skin cancer is the most common type of cancer but certainly not the most fatal. Although skin cancer most often occurs on areas of the
skin that are exposed to sunlight, this is not always the case.
There are three main types of skin cancer; melanoma, basal cell cancer and squamous cell cancer. Each develops from a different cell type of the skin's epidermal layer. Basal cell carcinoma and squamous cell carcinoma are the most common and most treatable if they are found early. Melanoma is a more serious form of skin cancer affecting deeper layers of the skin and has a higher potential to spread to other parts of the body. Risks of all three types of skin cancer are increasing. The National Cancer Institute estimates that there will be 1,000,000 new cases of non-melanoma cancer in the US in 2008 with less than 1,000 deaths due to these cancers. It is estimated that there will be 62,480 new melanomas cases diagnosed and 8,420 deaths in the US due to melanoma in 2008.
Basal cell cancer is the most common type of skin cancer, accounting for about 75% of all skin cancers. It develops from cells of the lowest layer of the epidermis, the basal cells. These are the cells which produce new skin cells. It occurs primarily on the parts of the skin exposed to the sun and is most common in people living in equatorial regions or areas of high ozone depletion. Light-skinned people are at greater risk of developing basal cell cancer than dark-skinned people. Basal cell cancer grows very slowly; however if it is not treated it can invade deeper skin layers causing extensive damage and can be fatal. This type of cancer can appear as a shiny, translucent nodule on the skin or as a red, wrinkled and scaly area.
Squamous cell cancer is the second most frequent type of skin cancer. It arises from the outer keratinizing layer of skin just below the surface. Squamous cell cancer grows faster than basal cell cancer and is more likely to metastasize to the lymph nodes as well as to distant sites. Squamous cell cancer most often appears on the arms, head, and neck. Fair-skinned people of Celtic descent are at high risk for developing squamous cell cancer. This type of cancer is rarely life-threatening but can cause serious problems if it spreads and can also cause disfigurement. Squamous cell cancer usually appears as a scaly, slightly elevated area of damaged skin. Squamous cell cancer can spear in an area of chronic inflammation on the skin.
Malignant melanoma is the most serious type of skin cancer. It develops from the melanocytes or pigment producing cells of the skin. These cells are found in the lower part of the epidermis. Melanocytes are stimulated by the sun to produce more melanin or pigment. It is this pigment that protects skin cells from sun damage and explains why darker skinned persons have a lower risk of melanoma. Although melanoma is the least common skin cancer, it is the most aggressive. It spreads (metastasizes) to other parts of the body—especially the lungs and liver—as well as invading surrounding tissues. Melanomas in their early stages resemble moles. In Caucasians, melanomas appear most often on the trunk, head, and neck in men and on the arms and legs in women. Melanomas in African Americans, however, occur primarily on the palms of the hand, soles of the feet, and under the nails. Melanomas appear only rarely in the eyes, mouth, vagina, or digestive tract. Although melanomas are associated with exposure to the sun, the greatest risk factor for developing melanoma might be genetic. People who have a first-degree relative with melanoma have an increased risk up to eight times greater of developing the disease.
Besides the three major types of skin cancer, there are a few other less common forms of skin cancer as well as some precancerous skin lesions.
- Kaposi's sarcoma (KS) occurs primarily in people whose immune system is depressed, such as AIDS patients, or those who have had organ transplants. When KS occurs with AIDS it is usually more aggressive.
- Merkel cell carcinoma is a rare skin cancer usually found on sun-exposed areas. Merket cell carcinoma grows more rapidly than basal and squamous cell carcinomas and can spread.
- Sebaceous gland carcinoma is an aggressive cancer that begins in the oil glands of the skin. They are hard, painless nodules that can develop anywhere, but most often on the eyelid.
Precancerous skin lesions include:
- Actinic keratosis or AK is also known as solar keratosis. It appears as rough, scaly patches that are red, pink or brown. They appear most often on the face, ears, lower arms and hands. This condition is not cancer but may develop into squamous cell carcinoma.
- Leukoplakia occurs inside the mouth as white patches. It is related to constant irritation as might be caused by smoking, rough edges on teeth, dentures or fillings.
- Actinic chelitis is a type of actinic keratosis or leukoplakia that occurs on the lips.
- Bowen's disease. This is a type of skin inflammation (dermatitis) that sometimes looks like squamous cell cancer. This may be a superficial type of squamous cell carcinoma that appears as a persistent, scaly patch. It can resemble eczema or psoriasis.
- Keratoacanthoma is a dome-shaped tumor that can grow quickly and appear like squamous cell cancer. Although it is usually benign, it should be removed.
The biggest risk for skin cancer is excessive exposure to the sun and getting sunburned. The risk of skin cancer is also hereditary, with the risk increasing with a first degree relative having the disease. Those who are fair skinned are more at risk. Age is also a risk factor as skin cancers tend to take years to develop they rarely appear before age 30 or 40. Melanoma is 10 times more likely to occur in whites than in African Americans. People having a high number of moles on their body are also at higher risk.
Exposure to toxic chemicals such as arsenic, tar, coal, paraffin and certain types of oil can increase the risk of non-melanoma skin cancer. Radiation therapy used for cancer as well as drugs used to treat psoriasis can also increase the risk of non-melanoma skin cancer. Skin cancer most often develops on areas of the skin that are exposed to the sun. The most common locations are the scalp, face, lips, ears, neck, chest, arms and hands. It can however also occur on areas that do not see much light such as the palms, between the toes and the genital area.
Risk factors for skin cancer include the following
- Excessive exposure to ultraviolet light or a history of sunburns. Severe sunburns as a child increases the risk for skin cancer later in life.
- Having fair skin or less pigmentation in the skin.
- A family history of skin cancer or a personal history of previously having skin cancer.
- Exposure to certain environmental chemicals including arsenic, pitch, creosote, radium or coal tar.
- Age—skin cancer takes years to develop and is more common with age. The sunburn you get as a teen can increase your risk of skin cancer when you are 40.
- A weakened immune system due to HIV/AIDS, leukemia, or drugs that suppress the immune system.
- Having a high number of moles on the body; more than 100.
Causes and symptoms
All three main types of skin cancer are related to excessive sun exposure. Ultraviolet light from the sun damages the DNA found in the cells. This damage to the DNA causes changes in the cell that can lead to increased and out of control growth. Although it was once thought that only UVB rays were responsible for the DNA damage that leads to cancer we now know it is both UVA and UVB rays. Since tanning beds deliver high levels of UVA, they can put people at significant risks.
Basal cell carcinoma appears as a pearly or waxy bump or a flat, flesh colored or brown mark. It is difficult to distinguish this type of mark from a normal mole without performing a biopsy. A basal cell carcinoma can take months or years before it becomes sizable. Squamous cell carcinoma can appear as a firm, red nodule or a flat mark with scaly, crusted surface.
Melanoma, the most serious of the skin cancers, appears as a large brownish spot. This spot can change in color or size or have an irregular border. It can also appear as a shiny, firm, dome-shaped bump. Melanomas can vary greatly in their appearance, but often the first sign is a change in a mole. Early detection of melanoma is important for successful treatment.
Kaposi sarcoma appears as red or purple patches on the skin or mucous membranes. This type of cancer tends to be more common in people with immune suppression such as those with AIDS or who have undergone organ transplants.
It used to be the ABCD rule was used as a guide for examining moles. Recently, the American Cancer Society added E to their visual grading system. This ABCDE system provides an easy way to remember the important characteristics of moles when one is examining the skin:
- Asymmetry. A normal mole is round, whereas a suspicious mole is unevenly shaped.
- Border. A normal mole has a clear-cut border with the surrounding skin, whereas the edges of a suspect mole are often irregular or scalloped.
- Color. Normal moles are uniformly tan or brown, but cancerous moles may appear as mixtures of red, white, blue, brown, purple, or black.
- Diameter. Normal moles are usually less than 5 millimeters in diameter. A skin lesion greater than 1/4 inch across may be suspected as cancerous.
- Evolving. A mole that changes over time in color or shape or develops itchiness or bleeding can be suspect.
A person who finds a suspicious-looking mole, a change in the appearance or texture of a mole, new areas of skin growth or a bothersome area of skin should consult a physician. As with many cancers, early detection and treatment is important in increasing the chances of treating the cancer successfully. A physician can do a thorough inspection of the skin, noting any suspicious looking areas. If any suspect areas are found, the patient's primary care physician will most likely refer him or her to a physician who specializes in skin diseases (a dermatologist ). A proper diagnosis of skin cancer requires that a biopsy or a small sample of skin be taken and analyzed by a lab. The skin sample is often done in the physician's office under local anesthesia .
If cancer is present, the stage of the cancer is then determined. This is a rating of how advanced the cancer is and will help determine the appropriate treatment for the cancer. Stages include stage 0, stage I, stage II, stage III, and stage IV, often with substages as well. Each stage represents a progressively larger sized tumor. Stage 0 refers to a precancerous lesion of suspicious cells and stage IV refers to a more severe tumor that has spread to other parts of the body.
Treatment depends upon the type of cancer and the severity. Basal cell carcinoma is fairly easy to treat when detected early as is squamous cell. There are four main types of treatment for skin cancer. They include surgery, radiation therapy, chemotherapy and photodynamic therapy. There are always new types of treatment being tested in clinical trials. One new type is biologic therapy which stimulates the patient's immune system to remove the cancer.
Surgery is often the best choice if the tumor is localized and easily removable. There are several different surgical procedures used. Excision surgery involves using a scalpel cutting around the tumor to remove it from the skin. This can also be done by shaving the tumor off the surface of the skin. Mohs micrographic surgery involves taking the skin lesion off in small sections and immediately examining it in the microscope to see when the surgery has gone deep enough to remove the cancerous cells. It is a more time consuming surgery though and not always available. Cryosurgery freezes and destroys the tumor cells. Laser surgery uses a laser beam to cut the skin to remove the tumor. Dermabrasion removes the upper layer of skin and can be used for very small superficial tumors.
Radiation therapy uses high energy x rays directed towards the tumor to kill cancer cells. It is often used for cancers that occur on the face or ears where reconstructive surgery would be difficult. It is also used primarily for the elderly since it can increase the long term risk of other types of cancers.
Chemotherapy refers to drugs taken internally either by injection or orally that travel through the bloodstream. Chemotherapy is intended to either stop the growth of cancer cells or to kill the cancer cells. Chemotherapy often has rather serious side effects as it affects other cells in the body besides the cancer cells. Occasionally, for non-melanoma skin cancers, the chemotherapy can be delivered in a cream form to use topically.
Photodynamic therapy uses both a drug and a laser to kill cancer cells. The drug is a photosensitizer which becomes active only after light of a specific wavelength from the laser contacts it. This allows more control over preventing damage to healthy tissue. Photodynamic therapy is relatively new and not always available.
Some studies have found that a diet high in antioxidant nutrients such as carotenoids, vitamins E and C and selenium can decrease the risk of skin cancer. These nutrients are found in diets high in fruits and vegetables. Low fat diets are also linked to lower rates of skin cancer.
Prognosis depends upon the type of cancer and its severity. Skin cancer is the most common type of cancer in the US but accounts for less than 1% of cancer deaths. Basal cell carcinoma is fairly easy to treat when caught early. Squamous cell carcinoma also is not usually serious and can be 100% treatable if caught early. If not caught early though it can be more difficult to treat and can cause some disfigurement. A small number of squamous cell carcinomas can spread to other organs.
Melanoma is a more serious type of skin cancer, however, if it is caught early is still curable. Melanoma is the most likely skin cancer to spread to other parts of the body which worsens the prognosis. According to the American Cancer Society, for stage I melanoma, the 5-year survival rates range from 92 to 99%. The 5-year survival rate for stage II melanomas is from 56–78%. The 5-year survival rate for stage III melanoma decreases to 50–68% and for stage IV melanoma, 5-year survival drops to 18%. Patients over the age of 70 typically have 5-year survival rates on the lower side.
Although one can never change his genes or hereditary risk of getting any type of cancer, there is a lot one can do to decrease his risk of getting skin cancer. Avoid prolonged exposure to the sun or sunburn. Recently, there has been some controversy in the area of sun exposure and cancer. Although there is a definite relationship to excessive sun exposure and skin cancer, the risk of sensible exposure to the sun may have been over exaggerated. Exposure to sunlight is necessary for our bodies to make vitamin D and vitamin D deficiencies have been increasing recently, putting people at risk of vitamin D deficiency diseases. Vitamin D has also been found to decrease the rate of several types of cancer. There is also some evidence that certain sunscreen ingredients may actually contribute to cancer risks. However, recommendations are still to prevent overexposure to the sun.
- Wear protective clothing (long sleeves and hat) while in the sun.
- Use sunscreen of at least 15 SPF when outside.
- Avoid being outside when the sun is brightest, between 10 a.m. and 4 p.m.
- Avoid tanning beds.
- Check your skin periodically for abnormal moles. The American Academy of Dermatologists recommends doing this on your birthday: “Check your birthday suit on your birthday.” Although this will not prevent skin cancer, early detection improves prognosis.
QUESTIONS TO ASK YOUR DOCTOR
- What are my various treatment options?
- Are there any clinical trials that would be relevant for my type of cancer?
- What supplements are ok to take during treatment?
- What is your experience in treating this type of cancer?
- What stage or how advanced is my cancer?
- What is the goal of treatment, to eradicate the cancer or to alleviate symptoms?
- Should I go to a specialized cancer center?
A caregiver might want to be observant of moles on a patient in areas that he or she cannot see, such as the back. If a mole looks suspicious, a physician should be consulted.
Moan, J., Porojnicu, A.C., Dahlback, A., Setlow, R.B., Addressing the health benefits and risks, involving vitamin D or skin cancer, or increased sun exposure. PNAS 2008; 105: http://www.pnas.org/cgi/reprint/0710615105v1
Holick, M.F., Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease. Am. Journ. Clin. Nutr. 2004; 80:1678S-1688S. http://www.ajcn.org/cgi/content/full/80/6/1678S
National Cancer Institute http://www.cancer.gov/cancertopics/pdq/treatment/skin/Patient/page3
Mayo Clinic http://www.mayoclinic.com/health/skincancer/DS00190/DSECTION=7
American Cancer Society, 1-800-ACS-2345, http://www.cancer.org.
Cindy L. Jones Ph.D.
Skin cancer is a disease in which rapidly multiplying, abnormal cells (cancer cells) are found in the outer layers of the skin.
for searching the Internet and other reference sources
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 will be diagnosed with skin cancer.
The skin often is called 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 also is a critically important barrier between people and such foreign invaders as bacteria. The skin is very personal: it is the first part of the body that people present to the world.
Types of Skin cancer
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-ma) and non-melanoma skin cancers. Nonmelanoma skin cancers are the most common cancers of the skin. They are also the most curable. Melanoma is much less common than nonmelanoma skin cancers, but it is far more aggressive and it is often lethal.
The outer layer of the skin is called the epidermis (ep-i-DER-mis). It consists of layers of flat, scaly cells called squamous (SQUAY-muss) cells, under which are round cells called basal cells. The deepest part of the epidermis consists of melanocytes (MEL-a-no-sites), which are the cells that give skin its color. Melanoma begins in the melanocytes.
Nonmelanoma Skin cancers
The two main types of nonmelanoma skin cancers 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.
How Skin cancer develops
Skin cancer begins with damage to the DNA of the cells in skin. DNA is information we inherit from our 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 a serious cancer because it has the ability to spread to other places in the body. Nonmelanoma skin cancers, however, tend to stay put and are less likely to spread.
ABCDs of Melanoma Screening
The American Academy of Dermatology recommends checking the skin on a regular basis for changes in moles, freckles, and beauty marks. Their ABCD system for recognizing changes:
- A: asymmetrical shape.
- B: border with ragged, blurred, or irregular shape.
- C: color variations.
- D: diameter greater than 6 millimeters (size of a pencil eraser).
Moles that match any of the ABCDs should be seen by a doctor.
Certain kinds of risk factors suggest who might be likely to develop cancer. A risk factor is anything that increases a persons chances of getting a disease like skin cancer.
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. But dark-skinned people still can 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.
Nonmelanoma Skin cancers
Most nonmelanoma skin cancers are caused by unprotected exposure of the area that has the cancer to ultra-violet radiation. Most of this radiation comes from sunlight, but it may also 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 skin cancers 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 skin cancers.
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 skin cancers can be hard to tell 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 a melanoma or a nonmelanoma skin cancer is suspected, the doctor will take a special sample of skin (a biopsy) from the abnormal area for examination under the microscope.
The first step in treating skin cancer is to stage it, that is, to decide whether and how far it might have spread. Staging a cancer is an important step in deciding what the best treatment for the patient is. It also helps to determine the patient’s prognosis (outlook for survival). The most common system used to stage skin cancers assigns a Roman numeral from 0 to IV to the cancer. So, for example, stage 0 means the cancer has not spread beyond the tissue beneath the skin; stage IV means that the cancer has spread to other organs such as the lung, liver, or brain, and is less likely to be curable.
Sunshine and Skin Cancer
Cumulative Effects of Tanning
Long-term exposure to the ultraviolet (UV) rays of the sun damages the body’s skin cells and can lead to cancer. For example, repeated sunburn and tanning cause the skin to wrinkle and to lose its ability to hold its shape. Dark patches called lentigos (len-TEE-goes) (age spots or liver spots) may appear, along with scaly precancerous growths and actual skin cancers. The sun’s UV radiation also increases a person’s risk of developing eye problems, including cataracts, which can cause blindness.
Burning and Peeling
Burning and peeling are signs that a person’s skin has been damaged. The sun can also damage the DNA of cells, and if a person is exposed to the sun (or other forms of UV light) over many years, skin cancer may result.
Sunglasses are an effective way of preventing sun damage to the eyes. But not just any sunglasses will do. The right kind of sunglasses are wrap-around UV-absorbant sunglasses, which block 99 to 100 percent of ultraviolet radiation. If the label on the glasses reads
- UV absorption up to 400 nm, or
- special purpose, or
- meets ANSI UV requirements
it means the glasses block at least 99 percent of UV rays. Whether the glasses are dark or light does not matter. The protection comes from an invisible chemical that is applied to the lenses. Any type of eyewear can be treated to make it UV-absorbant.
Fortunately, most nonmelanoma skin cancers 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 or chemotherapy (kee-mo-THER-a-pee). Chemotherapy refers to the use of anticancer drugs that can be injected into a vein in the arm or taken as tablets. In some precancerous conditions, chemotherapy may simply be placed directly on the skin as a cream.
Treatment for melanoma includes surgery and chemotherapy. Radiation therapy (which uses high-energy rays to kill cancer cells) is not usually used to treat the original melanoma that developed on the skin.
A popular anti-skin cancer slogan in Australia goes, “Slip on a shirt! Slap on a hat! Slop on some sunscreen! Seek shade!” The most important way of lowering the risk of nonmelanoma skin cancer is to stay out of the sun. This is especially important in the middle of the day, when sunlight is the 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 with an SPF factor of 15 or more on areas of the skin exposed to the sun. Wide-brimmed hats and wrap-around sunglasses with 99 to 100 percent ultraviolet absorption help to protect the eyes. Tanning booths should be avoided.
Scientists have made enormous progress in understanding how ultraviolet light damages DNA and how DNA changes cause normal skin cells to become cancerous. In addition, researchers are looking into ways of treating skin cancers by enlisting the patient’s immune system (the body’s defenses against tumors and infection) to fight cancer cells.
A new type of treatment being studied called photodynamic (fo-to-dy-NAM-ik) therapy treats tumor cells with a special chemical that makes them sensitive and then shines a laser light on them, which kills them. Drugs related to vitamin A are being studied for use with some skin cancers. But the treatment has side effects, and its benefits have not been conclusively demonstrated. Researchers studying melanoma in particular are experimenting with adding genes to cancer cells to make them more sensitive to drugs, to replace damaged genes, or to encourage the immune system to attack the abnormal cells.
The most important thing 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 (that is, to come back) in the first five years after treatment. A person who loves being in the sun will have to adjust to a life without sun worshipping. But except for staying out of the sun, almost everyone with skin cancer can go back to the life they had before they got cancer.
Murphy, Gerald P., et al. Informed Decisions: The Complete Book of Cancer Diagnosis, Treatment, and Recovery. New York: Viking, 1997.
U.S. National Cancer Institute (NCI), Bethesda, MD 20892. NCI coordinates the government’s cancer research programs and clinical trials. Its website posts What You Need to Know About fact sheets for skin cancer, melanoma, and moles and dysplastic nevi.
American Academy of Dermatology, 930 N. Meacham Road, Schaumberg, IL 60173. Provides information about the science and medicine of the skin. Telephone 888-462-DERM http://www.aad.org
American Cancer Society (ACS), 1599 Clifton Road N.E., Atlanta, GA 30329-4251. ACS has resource centers at its website for melanoma and nonmelanoma skin cancer. Telephone 800-ACS-2345 http://www3.cancer.org
OncoLink. The University of Pennsylvania’s Cancer Center Web site. A valuable store of information for patients about all aspects of cancer. http://www.cancer.med.upenn.edu
Skin cancer is a malignant growth on the outer layer of the skin. A malignant growth is one that has the potential to cause death. Skin cancers are often divided into two general groups: malignant melanomas and non-melanoma cancers.
The outer layer of the skin (the epidermis) contains three kinds of cells. Most of those cells are squamous cells. Cells near the bottom of the epidermis are called basal cells. And cells that provide pigment (color) to the skin are known as melanocytes (pronounced MELL-uh-no-sites).
Each type of cell can become cancerous. The three types of skin cancers, therefore, are squamous cell cancer, basal cell cancer, and malignant melanoma (cancer of the melanocytes). Malignant melanoma is by far the most serious form of skin cancer.
Other forms of skin cancer occur, but they are quite rare. The most serious of these is Kaposi's sarcoma (see Kaposi's sarcoma entry). At one time, Kaposi's sarcoma was very rare. It occurred primarily in older men of Mediterranean ancestry. It now occurs commonly in individuals with AIDS (see AIDS entry).
Exposure to sunlight is thought to be the major cause of skin cancers. About eight hundred thousand cases of squamous and basal cell cancers alone are diagnosed each year in the United States. The risk for skin cancers increases the closer one lives to the equator.
All forms of skin cancer begin with a single cell. For reasons that are usually not known, the cell begins to grow very rapidly. Its growth is soon out of control. It divides into two new cells, which continue growing wildly. Eventually the cancerous cells spread through a larger area. They can also begin to grow downward towards inner layers of the skin.
Malignant melanoma is the least common type of skin cancer. It is also the most aggressive. It spreads to surrounding tissues very quickly. It also invades other parts of the body, especially the lungs and liver.
Melanomas are probably caused by exposure to the sun. But they are also caused by genetic factors. A person is more likely to develop a melanoma if someone else in his or her family has also had the disorder.
Melanomas can occur anywhere on the body. Among Caucasians, they appear most often on the head, neck, arms, legs, and trunk of the body. Among African Americans, they occur primarily on the palms of the hands and the soles of the feet.
Basal Cell Cancer
Basal cell cancer is the most common form of skin cancer. It accounts for about 75 percent of all skin cancers. Light-skinned people are more likely to get the disease than are dark-skinned people. It usually appears after the age of thirty. Basal cell cancers grow very slowly, making them easier to treat than melanomas.
Squamous Cell Cancer
Squamous cell cancer is the second most common type of skin cancer. It grows more quickly than basal cell cancer, but less quickly than a melanoma. It can spread to other parts of the body, especially the lymph nodes. Lymph nodes are small round or oval bodies that are part of the body's immune system. Squamous cell cancer occurs most often on the arms, neck and head. This form of skin cancer is usually not life-threatening. But it can cause serious scarring.
Skin Cancer: Words to Know
- Not dangerous.
- Removal of a small piece of tissue for examination under a microscope.
- The outer layer of skin.
- A change in the structure or appearance of a part of the body as the result of an injury or infection.
- Lymph nodes:
- Small round or oval bodies within the immune system. Lymph nodes provide materials that fight disease and help remove bacteria and other foreign material from the body.
- Threatening to life.
- A specialized skin cell that produces melanin, a dark pigment (color) found in skin.
Heredity (the process by which genes are passed from one generation to another) is thought to be an important factor in the development of melanomas. For all forms of skin cancer, exposure to sunlight is probably the most important environmental factor. Research suggests that sunburns received early in one's childhood can lead to skin cancer later in life. A cancer usually does not show up until ten to twenty years after the sunburn has been received. For this reason, skin cancers seldom develop before a person reaches his or her twenties.
Other factors may also lead to skin cancer. For example, people who work with certain chemicals may be at risk for the disease. Also, people with weakened immune systems, such as those who have AIDS, may be more likely to develop some kinds of skin cancer.
All forms of skin cancer develop according to a similar pattern. The first sign of a cancer is usually a change in the appearance of an existing mole, the presence of a new mole, or a change in the appearance of an area of the skin.
Basal cell cancer usually appears as a small lesion (wound) in the skin that lasts for at least three weeks. The lesion (pronounced LEE-zhun) looks flat and waxy, with shiny, rounded edges. There may be a sore at the center of the lesion that makes it look like a dimple. The lesion slowly grows larger if it is not treated.
A squamous cell cancer generally begins as a small raised bump on the skin. The bump may have a sore at its center. It usually does not itch or cause pain.
A common symptom of melanoma is a change in an existing mole. The mole may change color, size or shape. It may become tender or itchy. If it starts to bleed, the cancer may already have begun to progress.
Specialists often recommend the ABCD rule in checking for melanomas. These letters come from the following steps:
- A symmetry. Moles are normally round. If a mole begins to take an unusual (asymmetric) shape, it may be cancerous.
- B order. A normal mole has a clear-cut border with the surrounding skin. A cancerous mole has an uneven border.
- C olor. Normal moles are tan or brown. A cancerous mole may be any mixture of red, white, blue, brown, purple, and/or black.
- D iameter. A normal mole is usually less than 5 millimeters (.25 inches) in diameter. Any mole that grows larger than that size may be cancerous.
Anyone who notices a suspicious-looking blemish on the skin should see a medical doctor. The doctor will ask about the history of the blemish, such as how long it has been there and whether it itches or bleeds, as well as other questions about the patient's health.
If a skin cancer is suspected, the doctor may take a biopsy of the blemish. A biopsy is a medical procedure in which a small sample of tissue is removed, usually with a thin needle. The tissue is then studied under a microscope. The presence of cancer cells can be detected with the microscope. The type of cancer present, if any, can be determined by the appearance of the cells.
It may also be necessary to determine how far the cancer has spread, if at all. Tests used to make this determination include X rays, blood tests, and various imaging tests. Imaging tests are tests used to study the composition and function of internal organs.
The usual procedure for treating any form of skin cancer is surgery. The doctor cuts out the mole or diseased area of the skin with a scalpel. A small section of healthy tissue surrounding the cancer is also removed. The reason that healthy tissue is removed is to make sure that all cancer cells have been eliminated.
Other methods can be used to kill and/or remove a cancer also. For example, the cancer may be frozen with dry ice or liquid nitrogen. The dead tissue can then be easily removed. Radiation treatments are sometimes recommended for older people or in cases where surgery is not possible or desirable. Surgical removal of a cancer may be followed by cosmetic surgery to hide the scars left by cutting or freezing.
Basal cell cancer and squamous cell cancer are generally treated successfully by these methods. Advanced cases of melanoma may require more aggressive treatment. This is especially true if the cancer has begun to spread through the body. It may be necessary, for example, to remove a person's lymph nodes if they have become cancerous. Radiation therapy may also be recommended if the melanoma has spread to other parts of the body.
There are no generally accepted alternative treatments for skin cancer. Some practitioners recommend therapies that may reduce one's risk for getting skin cancer. For example, they suggest a diet high in antioxidants, such as vitamins C and E. Antioxidants are chemicals that may slow down the growth of cancerous cells. Herbal remedies that may prevent skin cancer include natural antioxidants, such as bilberry, hawthorn, tumeric, and ginkgo.
Both basal cell and squamous cell cancer are curable when treated promptly. The key to success is early detection and treatment of the conditions. The cure rate for both forms of cancer is nearly 100 percent.
The prognosis for melanoma depends on how far the disease has spread. If a melanoma is removed in its early stages, the cure rate may be as high as 95 percent. If the cancer has spread to other parts of the body, the cure rate drops dramatically. If it has reached the lymph nodes, for example, the survival rate after five years is about 50 percent. If the condition has gone beyond the lymph nodes, it may be considered incurable.
Prevention is the best way to deal with all forms of skin cancer. The less one is exposed to sunlight, the less the risk of skin cancer. One way to avoid sunlight, of course, is simply to stay out of the sun. At the least, one should avoid the sun during the hottest part of the day, between 11 a.m. and 1 p.m When one is in the sun, he or she should use sunscreen with a protective factor of fifteen or more.
Regular self-examinations can also be helpful. A person should check once a month for unusual moles or other growths on the skin. If such growths are found, medical advice should be sought.
FOR MORE INFORMATION
Kenet, Barney J., and Patricia Lawler-Kenet. Saving Your Skin: Prevention, Early Detection, and Treatment of Melanoma and Other Skin Cancers. New York: Four Walls Eight Windows, 1998.
Lane, William I., and Linda Comac. The Skin Cancer Answer. Garden City Park, NY: Avery Publishing Group, 1999.
American Academy of Dermatology. 930 N. Meacham Road, Schaumburg, IL 60173. (847) 330–0230; (888) 462–DERM (3376).
National Cancer Institute. 31 Center Drive, Bethesda, MD 20892–2580. (800) 4–CANCER. http://www.nci.nih.gov.
Skin Cancer Foundation. PO Box 561, New York, NY 10156. (800) 754–6490.
"Ask NOAH About: Skin Cancer." NOAH: New York Online Access to Health. [Online] http://www.noah.cuny.edu/cancer/nci/cancernet/201228.html (accessed on October 31, 1999).
Cancer Care News. [Online] http://www.cancercarinc.org (accessed on November 4, 1999).
A skin biopsy is a procedure in which a small piece of living skin is removed from the body for examination, usually under a microscope, to establish a precise diagnosis. Skin biopsies are usually brief, straightforward procedures performed by a skin specialist (dermatologist) or family physician.
The word biopsy is taken from Greek words that mean "to view life." The term describes what a specialist in identifying diseases (pathologist) does with tissue obtained from a skin biopsy. The pathologist visually examines the tissue under a microscope.
A skin biopsy is used to make a diagnosis of many skin disorders. Information from the biopsy also helps the doctor choose the best treatment for the patient.
Doctors perform skin biopsies to:
- make a diagnosis
- confirm a diagnosis made from the patient's medical history and a physical examination
- check whether a treatment prescribed for a previously diagnosed condition is working
- check the edges of tissue removed with a tumor to make certain it contains all the diseased tissue
Skin biopsies also can serve a therapeutic purpose. Many skin abnormalities (lesions) can be removed completely during the biopsy procedure.
A patient taking aspirin or another blood thinner (anticoagulant) may be asked to stop taking them a week or more before the skin biopsy. This adjustment in medication will prevent excessive bleeding during the procedure and allow for normal blood clotting.
Some patients are allergic to lidocaine, the numbing agent most frequently used during a skin biopsy. The doctor can usually substitute another anesthetic agent.
The first part of the skin biopsy test is obtaining a sample of tissue that best represents the lesion being evaluated. Many biopsy techniques are available. The choice of technique and precise location from which to take the biopsy material are determined by factors such as the type and shape of the lesion. Biopsies can be classified as excisional or incisional. In excisional biopsy, the lesion is completely removed; in incisional biopsy, a portion of the lesion is removed.
The most common biopsy techniques are:
- Shave biopsy. A scalpel or razor blade is used to shave off a thin layer of the lesion parallel to the skin.
- Punch biopsy. A small cylindrical punch is screwed into the lesion through the full thickness of the skin and a plug of tissue is removed. A stitch or two may be needed to close the wound.
- Scalpel biopsy. A scalpel is used to make a standard surgical incision or excision to remove tissue. This technique is most often used for large or deep lesions. The wound is closed with stitches.
- Scissors biopsy. Scissors are used to snip off surface (superficial) skin growths and lesions that grow from a stem or column of tissue. Such growths are sometimes seen on the eyelids or neck.
After the biopsy tissue is removed, bleeding may be controlled by applying pressure or by burning with electricity or chemicals. Antibiotics often are applied to the wound to prevent infection. Stitches may be placed in the wound, or the wound may be bandaged and allowed to heal on its own.
The second part of the skin biopsy test is handling and examining the tissue sample. Drying and structural damage to the tissue sample must be prevented, so it should be placed immediately in an appropriate preservative, such as formaldehyde.
The pathologist can use a variety of laboratory techniques to process the biopsy tissue. Tissue stains and several different kinds of microscopes are used. Because there are many skin disorders (broadly called dermatosis and dermatitis ), the pathologist has extensive training in their accurate identification. Cases of melanoma, the most malignant kind of skin cancer, have almost tripled in the past 30 years. Because melanoma grows very rapidly in the skin, quick and accurate diagnosis is important.
The area of the biopsy is cleansed thoroughly with alcohol or a disinfectant containing iodine. Sterile cloths (drapes) may be positioned, and a local anesthetic, usually lidocaine, is injected into the skin near the lesion. Sometimes the anesthetic contains epinephrine, a drug that helps reduce bleeding during the biopsy. Sterile gloves and surgical instruments are always used to reduce the risk of infection.
If stitches have been placed, they should be kept clean and dry until removed. Stitches are usually removed five to 10 days after the biopsy. Sometimes the patient is instructed to put protective ointment on the stitches before showering. Wounds that have not been stitched should be cleaned with soap and water daily until they heal. Adhesive strips should be left in place for two to three weeks. Pain medications usually are not necessary.
Infection and bleeding occur rarely after skin biopsy. If the skin biopsy may leave a scar, the patient usually is asked to give informed consent before the test.
The biopsy reveals normal skin layers.
Dermatitis— A skin disorder that causes inflammation, that is, redness, swelling, heat, and pain.
Dermatologist— A doctor who specializes in skin care and treatment.
Dermatosis— A noninflammatory skin disorder.
Lesion— An area of abnormal or injured skin.
Pathologist— A person who specializes in studying diseases. In particular, this person examines the structural and functional changes in the tissues and organs of the body that are caused by disease or that cause disease themselves.
The biopsy reveals a noncancerous (benign) or cancerous (malignant) lesion. Benign lesions may require treatment.
American Academy of Dermatology. 930 N. Meacham Road, P.O. Box 4014, Schaumburg, IL 60168-4014. (847) 330-0230. Fax: (847) 330-0050. 〈http://www.aad.org〉.
skin cancer, malignant tumor of the skin. The most common types of skin cancer are basal cell carcinoma, squamous cell carcinoma, and melanoma. Rarer forms include mycosis fungoides (a type of lymphoma) and Kaposi's sarcoma. Overexposure to the sun is the primary cause of the common skin cancers, and the popularity of tanning since the 1930s lies behind the rise in skin cancer rates. The depletion of the earth's protective ozone layer also plays a role. The most effective way of preventing skin cancer is to avoid exposure to the sun's ultraviolet rays by consistently applying effective sunscreens (see sunburn) and wearing protective clothing.
Basal and Squamous Cell Carcinomas
Basal and squamous cell carcinomas are the most common types of cancer. Both arise from epithelial tissue (see epithelium). They are rare in dark-skinned people; light-skinned, blue-eyed people who do not tan well but who have had significant exposure to the rays of the sun are at highest risk. Both types usually occur on the face or other exposed areas.
Basal cell carcinoma typically is seen as a raised, sometimes ulcerous nodule. The nodule may have a pearly appearance. It grows slowly and rarely metastasizes (spreads), but it can be locally destructive and disfiguring. Squamous cell carcinoma typically is seen as a painless lump that grows into a wartlike lesion, or it may arise in patches of red, scaly sun-damaged skin called actinic keratoses. It can metastasize and can lead to death.
Basal and squamous cell carcinomas are easily cured with appropriate treatment. The lesion is usually removed by scalpal excision, curettage, cryosurgery (freezing), or micrographic surgery in which successive thin slices are removed and examined for cancerous cells under a microscope until the samples are clear. If the cancer arises in an area where surgery would be difficult or disfiguring, radiation therapy may be employed. Genetic scientists have discovered a gene that, when mutated, causes basal cell carcinoma.
Melanoma is the most virulent type of skin cancer and the type most likely to be fatal. As with the other common skin cancers, melanoma can be caused by exposure to the sun, and its incidence is increasing around the world. There also appears to be a hereditary factor in some cases. Although light-skinned people are the most susceptible, melanomas are also seen in dark-skinned people. Melanomas arise in melanocytes, the melanin-containing cells of the epidermal layer of the skin. Melanin is the pigment that gives skin color and that helps to protect the skin from sun damage. In light-skinned people, melanomas appear most frequently on the trunk in men and on the arms or legs in women. In blacks melanomas appear most frequently on the hands and feet. It is unknown whether melanoma in blacks is related to sun exposure. It is recommended that people examine themselves regularly for any evidence of the characteristic changes in a mole that could raise a suspicion of melanoma. These include asymmetry of the mole, a mottled appearance (variations in color from shades of brown to a bluish tint), irregular or notched borders, and oozing or bleeding or a change in texture. Surgery performed before the melanoma has spread is the only effective treatment for melanoma.
See publications of the National Cancer Institute and the American Cancer Society.
Skin cancer is the most common cancer in humans. There are three main types. Basal cell carcinoma is the most common, with over 1 million cases diagnosed in the United States in the year 2000. Basal cell carcinoma is locally destructive with an extremely low rate of metastasis. Squamous cell carcinoma is the second most common type of skin cancer. It is more lethal than basal cell carcinoma with an overall rate of metastasis of between 1 and 5 percent. Malignant melanoma is the most lethal form of skin cancer. With an incidence of nearly fifty thousand cases in the United States each year, melanoma results in nearly eight thousand fatalities, often striking young adults. Sun exposure is the major risk factor for the development of skin cancer. Surgical removal is the treatment of choice, and sun protection has been shown to dramatically reduce the incidence of this illness.
Gregg M. Menaker
(see also: Cancer; Melanoma; Ultraviolet Radiation )
Koh, H. K.; Barnhill, R. L.; and Rogers, G. S. (1996). "Melanoma." In Cutaneous Medicine and Surgery, eds. K. A. Arndt, P. E. Leboit, J. K. Robinson, and B. U. Weintroub. Philadelphia: W. B. Saunders.
Leshin, B., and White, W. (1996). "Malignant Neoplasms of Keratinocytes." In Cutaneous Medicine and Surgery, eds. K. A. Arndt, P. E. Leboit, J. K. Robinson, and B. U. Weintroub. Philadelphia: W. B. Saunders.