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Doctor checking mole on woman.

Skin Cancer Information

How Skin Cancer Forms

Cancer of the skin, like other cancers, is a disease of cells, which are small structures that make up all parts of the body. Cells organize into tissues, tissues organize into organs, and all the organs together make up the human body. Although cells differ in shape and function depending on the organ, all cells divide in order to heal the body and maintain normal body functions. Normal growth and repair of tissue is what keeps us healthy.

When cell division is not orderly and controlled, abnormal growth of cells occurs. A collection of abnormally dividing cells is called a tumor. Tumors can either be benign (non-cancerous) or malignant (cancerous). Benign tumors do not spread, but malignant tumors can invade and destroy surrounding normal tissue as they grow. Occasionally, cancer cells may break away from the tumor and spread (metastasize) either through the blood or lymphatic vessels to other parts of the body, where they form additional tumors. This is rare in most forms of skin cancer but can happen with melanoma if not detected early.

Types of Skin Cancer

There are three primary forms of skin cancer: basal cell carcinoma, squamous cell carcinoma, and malignant melanoma. Most cases of skin cancer are either basal cell carcinoma or squamous cell carcinoma. Each year there are more than 1 million cases of basal and squamous cell carcinoma diagnosed in the United States. Unfortunately, this number is on the rise.

Basal Cell Carcinoma

Basal cell carcinoma (BCC) is the most common type of skin cancer. In fact, it is the most common type of all cancers. Basal cell carcinoma arises from the bottom layer of the epidermis — the outermost layer of skin. It occurs more frequently on sun-exposed surfaces and typically grows more slowly than squamous cell carcinoma or malignant melanoma. It rarely spreads through the blood or lymphatic systems to other parts of the body.

Squamous Cell Carcinoma

Squamous cell carcinoma (SCC) is the second most common type of skin cancer. Squamous cell carcinoma arises from skin cells that are just above the basal layer of cells in the epidermis — the outermost layer of the skin. If left untreated, it has the potential to be more serious than basal cell carcinoma, since it has a greater ability to spread internally to nearby lymph nodes and to other parts of the body. Fortunately, most squamous cell carcinomas remain small and localized.

Malignant Melanoma

Malignant melanoma is one of the more serious types of skin cancer and can be life threatening if not detected and treated early. It usually appears as a brownish-black spot or bump in the skin. Typically the lesion either enlarges or changes in some way in its color, shape, or size. Sometimes the lesions may ulcerate and bleed. If you notice a changing mole, it is important to see a dermatologist for evaluation. Occasionally, melanomas arise in moles that have been present and stable for many years.

Signs of Skin Cancer

Although most skin growths are benign, any new growths on the skin, or a sore that does not heal, should be brought to your dermatologist's attention.

Skin cancer may appear in many different ways. It may begin as a small, pearly-waxy bump that may easily bleed or crust over. It could also be a dry, rough, scaling red spot. There is no one description that fits all skin cancers. The best way to catch a skin cancer early is to be mindful of lesions on your body and to develop a relationship with a dermatologist so that suspicious lesions can be spotted and dealt with in a timely manner. Although skin cancers usually start out small, they can grow to become very large, making treatment and cure more difficult.

Skin cancers sometimes arise from a non-cancerous skin condition called an actinic keratosis. This is a red, rough patch of skin that develops as a result of sun damage and is commonly found on the face, neck, or hands. Actinic keratosis can sometimes occur on the lips.

Causes of Skin Cancer

Exposure to the sun is the leading cause of skin cancer, which commonly develops on the face, neck and arms — the most sun-exposed areas of the body. Fair-skinned people with light hair and light eyes develop skin cancer more frequently than dark-skinned people. However, African-American and other dark-skinned people certainly can develop all types of skin cancer, including melanoma.

Certain people may also have a genetic susceptibility to developing skin cancer, and it occurs frequently in certain ethnic groups, particularly those with fair complexion such as northern Italians, Scandinavians and Celtics (especially Irish and Anglo-Saxons). Patients whose immune systems are suppressed after solid organ transplantation are at a much higher risk of developing skin cancer and should be closely monitored; skin cancers in this population can be particularly aggressive.

Other contributing factors to developing skin cancer include tanning bed use, ultraviolet light therapy, X-ray exposure, radiation therapy, chronic injury, burns, exposure to certain types of human papilloma (wart) viruses, exposure to certain chemicals including arsenic, and cigarette smoking.

Treatment of Skin Cancer

If your dermatologist thinks a skin growth may be cancerous, a biopsy is performed for definitive diagnosis by a dermatopathologist. The entire lesion or sometimes a portion of the lesion is removed surgically under local anesthesia and sent for examination under the microscope. The biopsy is used to confirm or rule out a diagnosis of cancer or to specify which type of cancer, if any, is found.

Several effective methods are used to treat skin cancer. The treatment method chosen depends on factors such as the location and type of cancer, its size, and whether or not previous therapies were attempted. Treatment methods available include surgical removal, curettage and electrodessication (scraping and burning with an electric needle), radiation therapy, cryosurgery with liquid nitrogen and Mohs micrographic surgery. Many of these treatments have acceptable cure rates. However, Mohs surgery uniformly produces the highest success rate, approaching 99%.

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Definitions for Commonly Used Words in Dermatology

Actinic keratosis – also called solar keratosis. A skin growth characterized by red, scaly areas, which occasionally become cancerous.

Basal cell carcinoma – the most common type of skin cancer. Basal cells are small, round cells found in the lowest part of the epidermis (the outermost layer of skin).

Benign tumor – a noncancerous growth that does not spread to other parts of the body.

Biopsy – the removal and microscopic examination of tissue from the body to obtain a definitive diagnosis.

Cancer – a general term for diseases characterized by abnormal and uncontrolled growth of cells. The resulting mass, or tumor, may invade and destroy surrounding normal tissue. Cancer cells from the tumor can spread through the blood or lymphatic system and affect other parts of the body.

Dermis – the second layer of skin, which contains blood vessels, nerves, collagen and elastic fibers.

Epidermis – the top, outermost layer of skin, in which both squamous and basal cells are found.

Local anesthetic – a substance that causes temporary loss of sensation and feeling when injected into a small, specific area of the body.

Lymph – a nearly colorless fluid that bathes the body's cells and moves through the lymphatic vessels of the body.

Melanoma – the least common but deadliest form of skin cancer. Melanoma is an abnormal growth of the cells in our bodies that produce pigment.

Metastasis – the spread of cancer through the blood or lymph from one part of the body to another.

Metastasize – to spread.

Squamous cell carcinoma – the second most common type of skin cancer. Squamous cells are small, flat structures that make up the majority of the skin's surface. Squamous cells are also referred to as keratinocytes.

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Helpful Links

From the American Academy of Dermatology

From the American Cancer Society

Find out today's UV index in your area from the U.S. Environmental Protection Agency UV index website.

The information on these pages is provided for general information only and should not be used for diagnosis or treatment, or as a substitute for consultation with a physician or health care professional. If you have specific questions or concerns about your health, you should consult your health care professional.

The images being used are for illustrative purposes only; any person depicted is a model.

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