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Squamous cell carcinoma is a common skin cancer that usually appears on sun-exposed areas of the body. In the vast majority of cases it is completely curable. Skin cancer is the most common cancer in the US. Squamous cell carcinoma (SCC) is the second most common skin cancer, following basal cell carcinoma. It can occur on all areas of the body, including the mucous membranes in the mouth and genitals; however, it most commonly arises on sun-exposed areas such as the face, arms, ears, hands, lips, neck, and scalp. More and more people develop skin cancer every year, possibly due to more people living longer, as well as greater populations residing in the sun belt.

The cancer develops in the outer layer of the skin (epidermis) in cells called squamous cells. Squamous cell carcinoma usually remains confined to the upper skin layers for some time, where it is relatively harmless. It can, however, penetrate deeper into the skin and occasionally spread (metastasize) to distant tissues and organs, significantly reducing the chance of a cure.
When squamous cell cancer is left untreated, it can expand laterally along the skin surface, penetrate deeper into the middle portion of the skin (the dermis), or grow along nerves or blood vessels. In some instances, SCC can spread to distant organs and tissues in the body via the lymphatic, nerve, or circulatory systems. Large SCCs; those on ears, lips, genitals, or backs of hands; and those that have developed over a prolonged period of time, have a greater risk of metastasis. While localized SCC can usually be easily removed, it is much harder to cure once it has spread in this fashion..
Experts believe that cumulative sun exposure over the years is the most likely cause for SCC, with an estimated 80% of lifetime exposure obtained before the age of 18.
Causes

SCC develops from the squamous cells of the epidermis. A series of increasingly abnormal changes can develop in the skin’s squamous cells. These changes occur when the cell’s DNA becomes altered (mutated). Subsequent generations of cells that grow from these damaged cells are then damaged themselves. Cell-damaging DNA mutations are usually the result of excessive exposure to sunlight. Other risk factors include radiation, arsenic exposure, burns, and chronic wounds.
Figure 1. Anatomy of the skin
Most skin cancers develop in the topmost layer of the skin (the epidermis). Basal cell carcinoma arises from the epithelial cells, the cells that comprise most of the epidermis.
The most common culprit for SCC is sun exposure, or more specifically, ultraviolet (UV) radiation. Damaging ultraviolet radiation occurs in two types: ultraviolet A (UVA) and ultraviolet B (UVB). UVB is the type of radiation primarily responsible for sunburn, and mainly affects the outer skin layers. UVA penetrates more deeply. Both have been implicated in the development of skin cancer.
Symptoms

The appearance of both SCC and its precursors can vary in color and size. SCC is often crusty or scaly, and may occasionally bleed. Actinic, or “solar” keratosis is a precancerous condition that may eventually develop into SCC if left untreated. It is usually less than 1 cm (.4 inches) in diameter, often has a scaly surface, and can vary in color from pink, red, or tan-brown. Because it may be the same color as the skin, it is sometimes noticeable only by its sandpaper-like texture. Sometimes it resembles a wart, and horn-like structures may develop on the surface. Occasionally, SCC can develop and grow rapidly if left untreated.

Another precencerous lesion is called actinic cheilitis. Actinic cheilitis gives a white, scaly appearance to the lip. It often involves the lower lip, which receives the most sun exposure. This, too, may develop into SCC if left untreated.
Figure 2. Actinic keratosis
Actinic, or “solar” keratosis is a precancerous condition that may eventually develop into SCC if left untreated. It is usually less than 1 cm (.4 inches) in diameter, often has a scaly surface, and can vary in color from pink, red, or tan-brown. Sometimes it resembles a wart, and horn-like structures may develop on the surface.
SCC that remains in the epidermis is known as Bowen’s disease, or squamous cell carcinoma in situ. Bowen’s disease may appear as a persistent, reddish-brown, scaly plaque that can resemble psoriasis or eczema, and may occasionally bleed. Although it does not invade deeper into the skin, it is a true skin cancer that requires treatment.
Figure 3. Bowen’s disease
Bowen’s disease may appear as a persistent, reddish-brown, scaly plaque that can resemble psoriasis or eczema, and may occasionally bleed.
More advanced carcinoma that has spread beyond the epidermis is often nodular, and may have open sores. This is vital Cancer Information

SCC can also develop inside the mouth, where it appears as a white, thickened area that may develop non-healing sores.
Lesions may also appear on the genital and anal regions, where they are often associated with a history of genital warts.
Table 1. Symptoms of Squamous Cell Carcinoma

Color: flesh-colored, pink, red, or brownSize: from microscopic to several centimeters in diameter, though usually less than 1 cm (.4 in)Sandpaper-like textureScalyCrustyMay grow horn-like structuresMay occasionally bleedMay form open soresOn lips: white, scalyOn mucous membrane (such as in mouth): whitish, thickened patchRisk Factors

Light-skinned individuals with a cumulative history of prolonged or intense sun exposure are at an increased risk of skin cancer. The incidence of skin cancer and its precursors increase dramatically with age. People who tend to burn rather than tan, those with light skin color, blond or red hair, freckles, and blue eyes are at especially high risk.
SCC tends to develop on people who have had excessive sun exposure: farmers, lifeguards, construction workers, outdoor enthusiasts, and others with a history of severe or frequent sunburns. Those who live at high altitudes or in areas where the ozone layer has thinned are also at increased risk. Immunocompromised people, including those with organ transplants, have a significantly increased risk of developing skin cancer.
Various other environmental factors have been implicated in SCC development.

• Tobacco: smokers have a 50% higher risk than nonsmokers
• Alcohol
• Treatment with UV radiation, as for psoriasis
• Treatment with x-rays
• Arsenic exposure

Skin cancer can also develop within burns or other chronic, nonhealing wounds.
Some people have an inherited predisposition to skin cancer, such as those with the genetic syndromes xeroderma pigmentosum (a hypersensitivity to UV light) and albinism (a deficiency or absence of melanin).
Diagnosis

Skin cancer is diagnosed upon clinical examination and confirmed by biopsy and microscopic examination of suspicious lesions. Most cases of SCC can be diagnosed clinically by a physician. The doctor will suspect either SCC or one of its precursors by the appearance and texture of the lesion. Characteristic microscopic findings of a biopsy of the lesion confirm the diagnosis.
In some cases, the doctor may biopsy or remove regional lymph nodes to help determine if the cancer has spread.
It is advisable to have the doctor thoroughly examine the rest of the skin to check for other suspicious lesions.
Prevention and Screening

Protection from excessive sun exposure--especially though frequent use of sunscreen with SPF 15 or higher, protective clothing, and avoiding the midday sun--is essential to reduce the risk of all types of skin cancer. Light-skinned individuals who burn easily should be especially cautious. The following precautions should be taken by everyone to guard against excessive exposure to UVA and UVB radiation.

• Try to schedule time outdoors for sports and other recreational activities before 10 AM and after 4 PM. By doing this you will avoid excessive exposure to UVA and UVB radiation. Clouds and haze do not completely block harmful ultraviolet radiation. It is not uncommon for a sunburn to develop on a cloudy day.
• When outdoors, wear clothes that cover as much skin as possible; such as lightweight, long-sleeved shirts, long pants, and a broad-brimmed hat.
• Use particular care around reflective surfaces, such as water, sand, concrete and white-painted areas.
• Everyone over 6 months of age should use a broad-based sunscreen that protects from UVA and UVB rays, and has a skin protection factor (SPF) of at least 15. Apply to exposed skin 20 minutes before exposure and reapply every two hours. More frequent re-application may be necessary with exercise or water-related activities.
• Zinc oxide and titanium dioxide are two ingredients that offer the best broad-spectrum protection from ultraviolet radiation.
• Infants should avoid direct sun exposure entirely to minimize risk for sunburn and long-term sun damage.
• There is no such thing as a “safe” or “healthy” tan. Avoid tanning booths or the use of sunlamps. Even though they emit mostly UVA rays and do not cause sunburn as frequently, they are associated with development of skin cancer, and promote premature aging of the skin.

Perform a regular skin self-examination in addition to having an annual skin examination by your physician. Experts recommend that individuals conduct a thorough screening of their own skin periodically. Have a partner check your back, or use a hand-held mirror to check your back and other hard-to-see places. Consider drawing a map of your body to indicate the location of moles, areas of discoloration, and other blemishes. Each month, note if a new growth has developed, or if there has been any change in shape, color, or size of lesions. See your doctor if you have any questions or suspicions.
At your annual checkup, ask your doctor to look at your skin, especially in areas you can’t see. People with major risk factors, such as a history of significant sun exposure, multiple moles, and a fair complexion with a history of burning easily, should be checked at least annually by a dermatologist.
Treatment

Self Care

Use sunscreen with SPF 15 or higher, wear protective clothing when in the sun, avoid being out in the midday sun, and check yourself regularly for new or changing skin lesions and non-healing sores.
Drug Therapy

Your doctor is the best source of information on the drug treatment choices available to you.
Other Therapies

In cases where surgical removal is impractical, radiation treatment is also effective. Radiation therapy can be very effective, and is occasionally used for difficult cases in which surgery would compromise the function of nearby structures (such as for a lesion on the eyelid or lip). Radiation is also useful in areas where cancer has recurred multiple times, and for elderly or ill patients for whom surgery may not be advisable. Typical radiation regimens are given several times a week for one to four weeks. Radiation may also be used to target lymph nodes if the doctor suspects that the disease has spread. Unfortunately, radiation therapy does not involve sampling tissue to confirm that the treatment was successful. Additionally, there is a long-term increased risk of developing a new skin cancer in the radiated site.
Phototherapy is another alternative for actinic keratoses. Phototherapy uses red or blue light to destroy actinic keratoses after the patient takes a special oral or topical medication (most commonly aminolevulinic acid) that selectively absorbs these wavelengths. Sunlight must be avoided for a given time around the pre- and post-treatment period. Phototherapy targets current lesions, but does not prevent future lesions from occurring.
Surgery

Surgical removal of skin cancer is the treatment of choice. A variety of surgical methods are available. Almost all surgical procedures for SCC are done on an outpatient basis in a doctor’s office using local anesthesia. They involve minimal pain and discomfort during and after the procedure.

• Simple excision of the lesion. A scalpel is used to excise the cancer as well as a thin border of the normal-appearing tissue to ensure that the entire cancer is removed.
• Electrosurgery. This method is used for very small and superficial lesions that are located on a flat skin surface such as the torso. The cancer is scraped away with a sharp, ring-shaped instrument called a curette, and the base of the lesion is cauterized with an electric wand.
• Mohs’ micrographic surgery. This method is used for lesions that occur on areas where tissue conservation is important, such as the eyelid, ear, lip, or nose. This method involves removing the visible tumor, and then removing a very thin layer of surrounding tissue. Each layer is processed in the office and examined under the microscope for residual cancer cells so that the doctor can determine when the entire tumor has been removed.
• Cryosurgery or laser surgery. Cryosurgery involves freezing the cancer or precancerous lesion with liquid nitrogen to destroy it. Laser surgery also destroys tissue and is sometimes used to treat actinic cheilitis (precancerous lesions on the lips).

Prognosis

The vast majority of SCCs are curable. Those that have already metastasized have reduced cure rates. Most squamous cell carcinomas are relatively slow-growing, and are discovered while they are still small and can be completely removed. Those that are most likely to metastasize tend to be large, occur on the lip, ear, or in the mouth, or show microscopic features of vascular or nerve involvement. Other factors that indicate more aggressive cancers are those associated with x-ray treatment and those arising within scars or nonhealing wounds. People who have immunosuppressive disorders, such as patients with organ transplants, leukemia, lymphoma, or AIDS, also tend to have more aggressive tumors.
Follow-up

Follow-up is essential after the treatment of SCC or any of its precursors. Even after the successful removal of an SCC, careful monitoring is important to determine whether or not the cancer has spread, and to monitor for development of a new skin cancer. Most doctors recommend follow-up every three to six months for the first two years after treatment. After that, the risk of metastasis is much lower, but close monitoring should be maintained. Individuals who have had actinic keratosis or skin cancer are at increased risk for developing further skin cancers.