Skin Cancer

The Skin

The skin is the body's outer covering. It protects us against heat, light, injury, and infection. It regulates body temperature and stores water, fat, and vitamin D. Weighing about 6 pounds, the skin is the body's largest organ. 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.

What Is Cancer?

Cancer is a group of more than 100 diseases. Although each type of cancer differs from the others in many ways, every cancer is a disease of some of the body's cells.
Healthy cells that make up the body's tissues grow, divide, and replace themselves in an orderly way. This process keeps the body in good repair. Sometimes, however, normal cells lose their ability to limit and direct their growth. They divide too rapidly and grow without any order. Too much tissue is produced, and tumor begin to form. Tumors can be benign or malignant.

• Benign tumors are not cancer. They do not spread to other parts of the body and are seldom a threat to life. Often, benign tumors can be removed by surgery, and they are not likely to return.
• Malignant tumors are cancer. They can invade and destroy nearby healthy tissues and organs. Cancer cells also can spread, or metastasize, to other parts of the body and form new tumors.

Types of Skin Cancer

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.

Cause and Prevention

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. Although anyone can get skin cancer, the risk is greatest for people who have fair skin that freckles easily--often those with red or blond hair and blue or light-colored eyes.

Ultraviolet radiation from the sun is the main cause of skin cancer. (Two types of ultraviolet radiation--UVA and UVB) 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. Worldwide, the highest rates of skin cancer are found in South Africa and Australia, areas that receive high amounts of UV radiation.

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 sunscreen can protect the skin. Sunscreens are rated in strength according to a SPF, which ranges from 2 to 30 or higher. Those rated 15 to 30 block most of the sun's harmful rays.

NCI is supporting research to try to find new ways to prevent skin cancer. This research involves people who have a high risk of developing skin cancer--those who have already had the disease and those who have certain other rare skin diseases that increase their risk of skin cancer.

Symptoms

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.

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

Detection

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.

Diagnosis

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.

Doctors generally divide skin cancer into two stages: local (affecting only the skin) or metastatic (spreading beyond the skin). Because skin cancer rarely spreads, a biopsy often is the only test needed to determine the stage. In cases where the growth is very large or has been present for a long time, the doctor will carefully check the lymph node in the area. In addition, the patient may need to have additional tests, such as special x-rays, to find out whether the cancer has spread to other parts of the body. Knowing the stage of a skin cancer helps the doctor plan the best treatment.

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