Introduction
Skin cancer is the most common form of human cancer. It is estimated that over 1 million new cases occur annually. The annual rates of all forms of skin cancer are increasing each year, representing a growing public concern. It has also been estimated that nearly half of all Americans who live to age 65 will develop skin cancer at least once.

The most common warning sign of skin cancer is a change in the appearance of the skin, such as a new growth or a sore that will not heal.

The term "skin cancer" refers to three different conditions. From the least to the most dangerous, they are:

• basal cell carcinoma (or basal cell carcinoma epithelioma)
• squamous cell carcinoma
• melanoma

The two most common forms of skin cancer are basal cell carcinoma and squamous cell carcinoma. Together, these two are also referred to as nonmelanoma skin cancer. Melanoma is generally the most serious form of skin cancer because it tends to spread (metastasize) throughout the body quickly.

This article will discuss the two kinds of nonmelanoma skin cancer. For information about melanoma, please read the Melanoma article.

Basal Cell Carcinoma

What is basal cell carcinoma?

Basal cell carcinoma is the most common form of skin cancer and accounts for more than 90 percent of all skin cancer in the U.S. These cancers almost never spread (metastasize) to other parts of the body. They can, however, cause damage by growing and invading surrounding tissue.

What are risk factors for developing basal cell carcinoma?

Light-colored skin and sun exposure are both important factors in the development of basal cell carcinomas. About 20 percent of these skin cancers, however, occur in areas that are not sun-exposed, such as the chest, back, arms, legs, and scalp. The face, however, remains the most common location for basal cell lesions. Weakening of the immune system, whether by disease or medication, can also promote the risk of developing basal cell carcinoma.

According to the U.S. National Institutes of Health, ultraviolet (UV) radiation from the sun is the main cause of skin cancer. Artificial sources of UV radiation, such as sunlamps and tanning booths, can also cause skin cancer. The risk of developing skin cancer is also affected by where a person lives. People who live in areas that receive high levels of UV radiation from the sun are more likely to develop 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, which are 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 in order to prevent skin cancer later in life.

What does basal cell carcinoma look like?

A basal cell carcinoma usually begins as a small, dome-shaped bump and is often covered by small, superficial blood vessels called telangiectases. The texture of such a spot is often shiny and translucent, sometimes referred to as "pearly." It is often hard to tell a basal cell carcinoma from a benign growth like a flesh-colored mole without performing a biopsy. Some basal cell carcinomas contain melanin pigment, making them look dark rather than shiny.

Basal cell carcinomas grow slowly, taking months or even years to become sizable. Although spread to other parts of the body (metastasis) is very rare, a basal cell carcinoma can damage and disfigure the eye, ear, or nose if it grows nearby.

How is basal cell carcinoma diagnosed?

To make a proper diagnosis, doctors usually remove all or part of the growth by performing a biopsy. This usually involves taking a sample by injecting a local anesthesia and scraping a small piece of skin. This method is referred to as a shave biopsy. The skin that is removed is then examined under a microscope to check for cancer cells.

How is basal cell carcinoma treated?

There are many ways to successfully treat a basal cell carcinoma with a good chance of success of 90% or more. The doctor's main goal is to remove or destroy the cancer completely with as small a scar as possible. To plan the best treatment for each patient, the doctor considers the location and size of the cancer, the risk of scarring, and the person's age, general health, and medical history.

Methods used to treat basal cell carcinomas include:

• Curettage and desiccation: Dermatologists often prefer this method, which consists of scooping out the basal cell carcinoma by using a spoon like instrument called a curette. Desiccation is the additional application of an electric current to control bleeding and kill the remaining cancer cells. The skin heals without stitching. This technique is best suited for small cancers in non-crucial areas such as the trunk and extremities.
• Surgical excision: The tumor is cut out and stitched up.
• Radiation therapy: Doctors often use radiation treatments for skin cancer occurring in areas that are difficult to treat with surgery. Obtaining a good cosmetic result generally involves many treatment sessions, perhaps 25 to 30.
• Cryosurgery: Some doctors trained in this technique achieve good results by freezing basal cell carcinomas. Typically, liquid nitrogen is applied to the growth to freeze and kill the abnormal cells.
• Mohs micrographic surgery: Named for its pioneer, Dr. Frederic Mohs, this technique of removing skin cancer is better termed, "microscopically controlled excision." The surgeon meticulously removes a small piece of the tumor and examines it under the microscope during surgery. This sequence of cutting and microscopic examination is repeated in a painstaking fashion so that the basal cell carcinoma can be mapped and taken out without having to estimate or guess the width and depth of the lesion. This method removes as little of the healthy normal tissue as possible. Cure rate is very high, exceeding 98%. Mohs micrographic surgery is preferred for large basal cell carcinomas, those that recur after previous treatment, or lesions affecting parts of the body where experience shows that recurrence is common after treatment by other methods. Such body parts include the scalp, forehead, ears, and the corners of the nose. In cases where large amounts of tissue need to be removed, the Mohs surgeon sometimes works with a plastic (reconstructive) surgeon to achieve the best possible post-surgical appearance.

How is basal cell carcinoma prevented?

Avoiding sun exposure in susceptible individuals is the best way to lower the risk for all types of skin cancer. Regular surveillance of susceptible individuals, both by self-examination and regular physical examination, is also a good idea for people at higher risk. People who have already had any form of skin cancer should have regular medical checkups.

Common sense preventive techniques include:

• Limiting recreational sun exposure
• Avoiding unprotected exposure to the sun during peak radiation times (the hours surrounding noon)
• Wearing broad-brimmed hats and tightly-woven protective clothing while outdoors in the sun
• Regularly using a waterproof or water resistant sunscreen with UVA protection and SPF number of 30 or higher
• Undergoing regular checkups and bringing any suspicious-looking or changing lesions to the attention of the doctor

Squamous Cell Carcinoma

What is squamous cell carcinoma?

Squamous cell carcinoma is cancer that begins in the squamous cells, which are thin, flat cells that look like fish scales under the microscope. The word "squamous" came from the Latin squama, meaning "the scale of a fish or serpent."

Squamous cells are found in the tissue that forms the surface of the skin, the lining of the hollow organs of the body, and the passages of the respiratory and digestive tracts. Thus, squamous cell carcinomas can actually arise in any of these tissues.

Squamous cell carcinoma of the skin occurs roughly one-quarter as often as basal cell carcinoma. Light-colored skin and a history of sun exposure are even more important in predisposing to this kind of cancer than to basal cell carcinoma. Men are affected more often than women. Patterns of dress and hairstyle may play a role. Women, whose hair generally covers their ears, develop squamous cell carcinomas far less often in this location than do men.

What are risk factors for developing squamous cell carcinoma?

The single most important factor in producing squamous cell carcinomas is sun exposure. Many such growths can develop from precancerous spots, called actinic or solar keratoses. These lesions appear after years of sun damage on parts of the body like the forehead and cheeks, as well as the backs of the hands. Sun damage takes many years to promote skin cancer. It is therefore common for people who stopped being "sun worshipers" in their twenties to develop precancerous or cancerous spots decades later.

Several rather uncommon factors may predispose to squamous cell carcinoma. These include exposure to arsenic, hydrocarbons, heat, or x-rays. Some squamous cell carcinomas arise in scar tissue. Suppression of the immune system by infection or drugs may also promote such growths.
Can squamous cell carcinoma of the skin spread (metastasize)?

Yes. Unlike basal cell carcinomas, squamous cell carcinomas can metastasize, or spread to other parts of the body. These tumors usually begin as firm, skin-colored or red nodules. Squamous cell cancers that start out within solar keratoses or on sun damaged skin are easier to cure and metastasize less often than those that develop in traumatic or radiation scars. One location particularly prone to metastatic spread is the lower lip. A proper diagnosis in this location is, therefore, especially important.

How is squamous cell carcinoma diagnosed?

As with basal cell carcinoma, make a proper diagnosis doctors usually performs a biopsy. This involves taking a sample by injecting local anesthesia and punching out a small piece of skin using a circular punch blade. Usually the method used referred to as a punch biopsy. The skin that is removed is then examined under a microscope to check for cancer cells.

Techniques for treating squamous cell carcinoma are similar to those for basal cell carcinoma (for detailed descriptions, see above under treatment of basal cell carcinoma):

• Curettage and desiccation: Dermatologists often prefer this method, which consists of scooping out the basal cell carcinoma by using a spoon like instrument called a curette. Desiccation is the additional application of an electric current to control bleeding and kill the remaining cancer cells. The skin heals without stitching. This technique is best suited for small cancers in non-crucial areas such as the trunk and extremities.
• Surgical excision: The tumor is cut out and stitched up.
• Radiation therapy: Doctors often use radiation treatments for skin cancer occurring in areas that are difficult to treat with surgery. Obtaining a good cosmetic result generally involves many treatment sessions, perhaps 25 to 30.
• Cryosurgery: Some doctors trained in this technique achieve good results by freezing basal cell carcinomas. Typically, liquid nitrogen is applied to the growth to freeze and kill the abnormal cells.
• Mohs micrographic surgery: Named for its pioneer, Dr. Frederic Mohs, this technique of removing skin cancer is better termed, "microscopically controlled excision." The surgeon meticulously removes a small piece of the tumor and examines it under the microscope during surgery. This sequence of cutting and microscopic examination is repeated in a painstaking fashion so that the basal cell carcinoma can be mapped and taken out without having to estimate or guess the width and depth of the lesion. This method removes as little of the healthy normal tissue as possible. Cure rate is very high, exceeding 98%. Mohs micrographic surgery is preferred for large basal cell carcinomas, those that recur after previous treatment, or lesions affecting parts of the body where experience shows that recurrence is common after treatment by other methods. Such body parts include the scalp, forehead, ears, and the corners of the nose. In cases where large amounts of tissue need to be removed, the Mohs surgeon sometimes works with a plastic (reconstructive) surgeon to achieve the best possible post-surgical appearance.

The possibility of metastasis makes it especially important to diagnose squamous cell carcinomas early and treat them adequately.

How is squamous cell carcinoma prevented?

Even more so than is the case with basal cell carcinoma, the key principles of prevention are minimizing sun exposure and getting regular checkups.

Common sense preventive techniques are the same as for basal cell carcinoma and include:

• Limiting recreational sun exposure
• Avoiding unprotected exposure to the sun during peak radiation times (the hours surrounding noon)
• Wearing broad-brimmed hats and tightly-woven protective clothing while outdoors in the sun
• Regularly using a waterproof or water resistant sunscreen with UVA protection and SPF number of 30 or higher
• Undergoing regular checkups and bringing any suspicious-looking or changing lesions to the attention of a doctor

What about follow-up care for skin cancer?

Skin cancer has a better prognosis, or outcome, than most other types of cancer. It is generally curable. Even though most skin cancers are cured, people who have been treated for skin cancer have a higher-than-average risk of developing a new cancer of the skin. This is the reason why it is so important for patients to continue to examine themselves regularly, visit their doctor for regular checkups, and follow their doctor's instructions on how to reduce their risk of developing skin cancer again.

Skin Cancer At A Glance

• There are three main types of skin cancer; basal cell carcinoma and squamous cell carcinoma (the nonmelanoma skin cancers), and melanoma.
• Skin cancer is the most common form of cancer in humans.
• Ultraviolet light, which is in sunlight, is the main cause of skin cancer.
• The most common warning sign of skin cancer is a change in the appearance of the skin, such as a new growth or a sore that will not heal. Unexplained changes in the appearance of the skin lasting longer than 2 weeks should be evaluated by a doctor.
• Nonmelanoma skin cancer is generally curable. The cure rate for nonmelanoma skin cancer could be 100% if these lesions were brought to a doctor's attention before they had a chance to spread.
• Treatment of nonmelanoma skin cancer depends on the type and location of the skin cancer, the risk of scarring, as well as the age and health of the patient. Methods used include curettage and desiccation, surgical excision, cryosurgery, radiation, and Mohs micrographic surgery.
• Avoiding sun exposure in susceptible individuals is the best way to lower the risk for all types of skin cancer. Regular surveillance of susceptible individuals, both by self-examination and regular physical examination, is also a good idea for people at higher risk. People who have already had any form of skin cancer should have regular medical checkups.

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