article syndicated from NCI
updated about 1 year ago
There are several types of skin cancer. The most common forms of skin cancer are basal cell carcinoma followed by squamous cell carcinoma. These forms are often referred to as nonmelanoma skin cancer to differentiate them from a third type, melanoma, which is less common, more deadly, and more likely to spread throughout the body.
Basal Cell Carcinoma and Squamous Cell Carcinoma
It is estimated that nonmelanoma skin cancer is on the rise and that 1 million cases will occur each year. Exact numbers of nonmelanoma skin cancer cases are not readily available because most are treated in doctors’ offices and may not be reported to cancer registries. Researchers estimate that 40 to 50 percent of people in the United States who live to age 65 will have nonmelanoma skin cancer at least once. The risk is highest for fair-skinned people with red or blond hair and light-colored eyes.
Ninety percent of all skin cancers in the United States are basal cell carcinoma. This type of cancer grows slowly and rarely spreads to other areas. It is typically found on the head, face, neck, hands, and arms but can occur anywhere. Squamous cell carcinoma also rarely spreads but is more likely to do so than basal cell carcinoma. Despite a fatality rate of less than one percent, these cancers should be treated because they can invade and destroy nearby tissue.
The main cause of nonmelanoma skin cancer is ultraviolet (UV) radiation from the sun or artificial sources such as sunlamps or tanning booths. An individual’s risk appears to involve geographic location. People who in live in areas with higher levels of UV radiation from the sun, such as those living closer to the equator, have higher risk. Lifetime exposure to UV radiation is also a risk factor. Damage can occur early in life, but most skin cancers appear after age 50 as a result of cumulative UV exposure.
The appearance of skin cancer is not always the same. It may be a small, smooth, shiny, pale, or waxy lump or a firm red lump. Some people develop a precancerous condition called actinic keratosis, a rough, red or brown scaly patch on the skin that may develop into squamous cell carcinoma. It usually occurs in areas that have been exposed to the sun, such as the face, the back of the hands, and the lower lip.
By conducting a monthly skin self-exam, people may notice a new area on the skin that may be suspicious and should consult a doctor. In addition, a doctor may notice a possible skin cancer or precancerous lesion during a routine examination. However, not all suspicious moles or skin conditions are skin cancer. Skin cancers can be diagnosed with a biopsy, in which the lesion is removed and examined by a pathologist. If the cancer has not spread, no further treatment may be necessary.
The primary way to prevent skin cancer is for people to reduce exposure to UV radiation. This involves avoiding the midday sun and artificial UV sources such as tanning beds, wearing protective clothing such as hats and sunglasses, and using sunscreens. Researchers have found that sunscreens are effective in protecting people from DNA damage in the skin due to UV exposure1. Daily sunscreen use reduces the incidence of actinic keratosis2. Clinical evidence suggests it is better to use sunscreens with both UVA and UVB protection than those with UVB alone. UVB rays are more likely than UVA rays to cause sunburn, but UVA rays pass more deeply into the skin. Sunscreen effectiveness may depend upon using it as directed, which includes liberal application and reapplication after water exposure or excessive perspiration. Sunscreens should be used in conjunction with other methods of avoiding UV exposure as mentioned above.
Certain clothing is made from sun-protective fabrics, which are usually darker and have a tighter weave than other fabrics. Sun-protective clothing is labeled with an Ultraviolet Protection Factor from 15 to 50, depending upon how much UV radiation passes through the fabric. The Federal Trade Commission has further information regarding these products.
Researchers are studying individuals who have an increased risk of skin cancers to find new ways to prevent and detect the development of skin cancer.
Most treatments for skin cancer currently involve some kind of surgery. Often skin cancer is removed completely during biopsy with no further treatment required. Most nonmelanoma skin cancers are curable, but people who have had skin cancer have a higher than average risk of developing another skin cancer.
Melanoma is a disease of pigment cells, or melanocytes, and typically occurs in the skin. Melanoma also occurs infrequently in the eyes, digestive tract, lymph nodes, or other areas where there are melanocytes. It is one of the most commonly occurring invasive cancers, affecting people of all ages, and incidence rates are increasing.
The rate of new melanoma cases increased from 1973 to 1998, although the rate of increase has slowed since 19813. According to the most recent data from the Surveillence, Epidemiology and End Results (SEER) program, NCI’s authoritative source of information on cancer incidence and survival in the United States, for every 100,000 people in the United States, there are 17.7 new cases of melanoma each year. Incidence is higher for men than for women overall, but young women have higher rates than young men. The overall incidence rate for men is 22.5 per 100,000 men compared with 14.4 per 100,000 for women. The death rate is 2.7 per 100,000. Five years after diagnosis, 89.6 percent survive either in remission, disease-free, or under treatment. Women have a 1.25 percent lifetime risk of being diagnosed while men have a lifetime risk of 1.77 percent.
Melanoma sometimes appears as a change in an existing mole or as a new mole. It comes in a variety of shapes and colors. Regular skin self-exams help people recognize what their moles look like so they can notice changes. Melanoma may develop on any skin surface. For men, the most common areas are the trunk, and to a lesser extent the head and neck. For women, the most common area is the lower legs followed by the trunk. Melanoma is rare in people with dark skin, but they may develop it under fingernails or toenails, or on palms or soles of the feet where the skin is lighter. Melanoma may also spread throughout the lymph nodes to other parts of the body.
People can use the ABCD (Asymmetry, Border, Color, Diameter) method when looking for mole characteristics that may indicate melanoma:
- Asymmetry - The shape of one half does not match the other.
- Border - The edges are ragged, notched, blurred, or irregular in outline or the pigment may spread into the surrounding skin.
- Color - Uneven color with shades of black, brown, and tan or areas of white, gray, red, pink, or blue may be visible. Occasionally, melanoma can be the same color as the rest of the skin.
- Diameter - There is a change in size. Melanomas are usually larger than the eraser of a pencil, but may be smaller.
Since melanoma moles do not all look the same, if you see anything suspicious, you should have a doctor examine it. The only way to definitively diagnose melanoma is with a biopsy, which involves a doctor removing all or part of the growth so that a pathologist might examine it for cancer cells.
The exact causes of melanoma are unknown. However, risk factors include having atypical moles known as dysplastic nevi; many moles; fair skin; personal history of melanoma or other skin cancer; family history of melanoma; weakened immune system; experiencing severe blistering sunburns; and exposure to UV radiation. The disease is more common in people who live in areas that get large amounts of UV radiation from the sun, such as people living near the equator. UV radiation from artificial sources such as sunlamps and tanning booths can also damage the skin and increase melanoma risk.
To prevent melanoma, people, particularly children and young adults, are often urged to follow the same precautions as those used to prevent nonmelanoma skin cancer, such as avoiding UV exposure and wearing protective clothing and sunscreen.
Melanoma treatments depend on the stage of the cancer at diagnosis. Melanoma can be cured if it is diagnosed and treated when the tumor is thin and has not deeply invaded the skin. When a melanoma becomes thick and deep, the disease often spreads to other parts of the body and is difficult to control. The most common treatment for melanoma is surgery to remove the tumor, which is most successful for people in early stages. Chemotherapy drugs are also sometimes used to kill the cancer cells, as is immunotherapy, which uses cytokines, a component of the body’s own immune system, to fight the cancer. Patients with metastatic melanoma, where the melanoma has spread to other organs, may be treated with interferon alpha and interleukin-2 (IL-2), which stimulates the growth and activity of immune cells that can destroy cancer cells. Clinical trials of new experimental treatments for people with advanced stages of melanoma are currently being conducted. These include work with therapeutic melanoma vaccines designed to help the immune system recognize and attack the cancer cells without harming normal cells. More information about clinical trials using experimental melanoma treatments can be found at http://www.clinicaltrials.gov.
- Ananthaswamy, H N. et al. Inhibition of Solar Simulator-Induced p53 Mutations and Protection Against Skin Cancer Development in Mice by Sunscreens. Journal of Investigative Dermatology 112:763-768, 1999.
- Darlington, S, et al. A Randomized Controlled Trial of assess Sunscreen Application and Beta Carotene Supplementaiton in the Prevention of Solar Keratoses. Archives of Dermatology. 139: 451-455, 2003.
- National Cancer Institute. 2001 Cancer Progress Report. http://progressreport.cancer.gov/
Scotto, J. Risk Factors: Skin (Nonmelanoma). Biostatistics Branch. National Cancer Institute.
Federal Trade Commission. Sun-Protective Clothing: Wear It Well.
http://www.ftc.gov. May 2001
National Cancer Institute. What You Need to Know About Melanoma.
http://www.cancer.gov/cancerinfo/wyntk/melanoma. Updated 3/31/2003.
National Cancer Institute. What You Need to Know About Skin Cancer.
http://www.cancer.gov/cancerinfo/wyntk/skin. Updated 9/16/2002.
NCI Resources on Skin Cancer
NCI Resources on Melanoma
The National Cancer Institute (NCI) is a component of the National Institutes of Health (NIH), one of eight agencies that compose the Public Health Service (PHS) in the Department of Health and Human Services (DHHS). The NCI, established under the National Cancer Act of 1937, is the Federal Government’s principal agency for cancer research and training.