The skin is the body’s outer covering. It is made up of two main layers: the outer epidermis and the inner dermis.
The epidermis (outer layer of the skin) is mostly made up of flat, scale-like cells called squamous cells. Under the squamous cells are round cells called basal cells. The deepest part of the epidermis also contains melanocytes. These cells produce melanin, which gives the skin its color.
The dermis (inner layer of skin) contains blood and lymph vessels, hair follicles, and glands. These glands produce sweat, which helps regulate body temperature, and sebum, an oily substance that helps keep the skin from drying out. Sweat and sebum reach the skin’s surface through tiny openings called pores.
Skin cancer is the most common type of cancer in the United States. According to current estimates, 40 to 50 percent of Americans who live to age 65 will have skin cancer at least once.
The two most common kinds of skin cancer are basal cell carcinoma and squamous cell carcinoma. (Carcinoma is cancer that begins in the cells that cover or line an organ.)
- Basal cell carcinoma accounts for more than 90 percent of all skin cancers in the United States. It is a slow-growing cancer that seldom spreads to other parts of the body.
- Squamous cell carcinoma also rarely spreads, but it does so more often than basal cell carcinoma. However, it is important that skin cancers be found and treated early because they can invade and destroy nearby tissue.
Basal cell carcinoma and squamous cell carcinoma are sometimes called nonmelanoma skin cancer.
Another type of cancer that occurs in the skin is melanoma, which begins in the melanocytes. Melanoma is the most serious cancer of the skin, and can can occur on any skin surface. In men, it is often found on the trunk (the area from the shoulders to the hips) or the head and neck. In women, melanoma often develops on the lower legs.
Melanoma can be cured if it is diagnosed and treated when the tumor is thin and has not deeply invaded the skin. However, if a melanoma is not removed at its early stages, cancer cells may grow downward from the skin surface, invading healthy tissue. When a melanoma becomes thick and deep, the disease often spreads to other parts of the body and is difficult to control.
Cause and Prevention
Ultraviolet (UV) radiation from the sun is the main cause of skin cancer, although artificial sources of UV radiation, such as sunlamps and tanning booths, can also cause skin cancer.
The risk of developing skin cancer is affected by where a person lives. People who live in areas that get high levels of UV radiation from the sun are more likely to get skin cancer. In the United States, for example, skin cancer is more common in Texas than it is in Minnesota, where the sun is not as strong.
In addition, skin cancer is related to lifetime exposure to UV radiation. Most skin cancers appear after age 50, but the sun’s damaging effects begin at an early age. Therefore, protection should start in childhood to prevent skin cancer later in life.
Whenever possible, people should avoid exposure to the midday sun (from 10 a.m. to 2 p.m. standard time, or from 11 a.m. to 3 p.m. daylight saving time). Keep in mind that protective clothing, such as sun hats and long sleeves, can block out the sun’s harmful rays. Also, lotions that contain sunscreens can protect the skin. Sunscreens are rated in strength according to a sun protection factor (SPF), which ranges from 2 to 30 or higher. Those rated 15 to 30 block most of the sun’s harmful rays.
The most common warning sign of skin cancer is a change on the skin, especially a new growth or a sore that doesn’t heal. Skin cancers don’t all look the same. For example, the cancer may start as a small, smooth, shiny, pale, or waxy lump. Or it can appear as a firm red lump. Sometimes, the lump bleeds or develops a crust. Skin cancer can also start as a flat, red spot that is rough, dry, or scaly.
Both basal and squamous cell cancers are found mainly on areas of the skin that are exposed to the sun — the head, face, neck, hands, and arms. However, skin cancer can occur anywhere.
Actinic keratosis, which appears as rough, red or brown scaly patches on the skin, is known as a precancerous condition because it sometimes develops into squamous cell cancer. Like skin cancer, it usually appears on sun-exposed areas but can be found elsewhere.
Often, the first sign of melanoma is a change in the size, shape, color, or feel of an existing mole. Most melanomas have a black or blue-black area. Melanoma also may appear as a new, black, abnormal, or “ugly-looking” mole. Other frequent findings are newly formed fine scales or itching in a mole. In more advanced melanoma, the texture of the mole may change. For example, it may become hard or lumpy.
Changes in the skin are not sure signs of cancer; however, it is important to see a doctor if any symptom lasts longer than 2 weeks. Don’t wait for the area to hurt — skin cancers seldom cause pain.
Detection and Diagnosis
The cure rate for skin cancer could be 100 percent if all skin cancers were brought to a doctor’s attention before they had a chance to spread. Therefore, people should check themselves regularly for new growths or other changes in the skin. Any new, colored growths or any changes in growths that are already present should be reported to the doctor without delay.
Doctors should also look at the skin during routine physical exams. People who have already had skin cancer should be sure to have regular exams so that the doctor can check the skin — both the treated areas and other places where cancer may develop.
Basal cell carcinoma and squamous cell carcinoma are generally diagnosed and treated in the same way. When an area of skin does not look normal, the doctor may remove all or part of the growth. This is called a biopsy. To check for cancer cells, the tissue is examined under a microscope by a pathologist or a dermatologist. A biopsy is the only sure way to tell if the problem is cancer.
If the doctor suspects that a spot on the skin is melanoma, the patient will need to have a biopsy, and the doctor will try to remove all of the suspicious-looking growth. If the growth is too large to be removed entirely, the doctor removes a sample of the tissue. Sometimes it is helpful for more than one pathologist to look at the tissue to determine whether melanoma is present.
Treating Skin Cancer
Many skin cancers can be cut from the skin quickly and easily. In fact, the cancer is sometimes completely removed at the time of the biopsy, and no further treatment is needed.
If melanoma is found, however, the doctor needs to learn the extent, or stage, of the disease before planning treatment. The treatment plan takes into account the location and thickness of the tumor, how deeply the melanoma has invaded the skin, and whether melanoma cells have spread to nearby lymph nodes or other parts of the body. Removal of nearby lymph nodes for examination under a microscope is sometimes necessary. (Such surgery may be considered part of the treatment because removing cancerous lymph nodes may help control the disease.) The doctor also does a careful physical exam and, depending on the thickness of the tumor, may order chest x-rays; blood tests; and scans of the liver, bones, and brain.
People with melanoma are often treated by a team of specialists, which may include a dermatologist, surgeon, medical oncologist, and plastic surgeon. The standard treatment for melanoma is surgery; in some cases, doctors may also use chemotherapy, biological therapy, or radiation therapy. The doctors may decide to use one treatment method or a combination of methods.
Even though most skin cancers are cured, the disease can recur in the same place. Also, people who have been treated for skin cancer have a higher-than-average risk of developing a new cancer elsewhere on the skin. That’s why it is so important for them to continue to examine themselves regularly, to visit their doctor for regular checkups, and to follow the doctor’s instructions on how to reduce the risk of developing skin cancer again.
Melanoma patients have a high risk of developing separate new melanomas. Some also are at risk for a recurrence of the original melanoma in nearby skin or in other parts of the body. To increase the chance that a new melanoma will be detected as early as possible, patients should follow their doctor’s schedule for regular checkups.
Background information provided by: National Cancer Institute, National Institutes of Health, Bethesda, MD 20892