Squamous cell carcinoma (SCC), the second most common skin cancer after basal cell carcinoma, afflicts more than 200,000 Americans each year. It arises from the epidermis and resembles the squamous cells that comprise most of the upper layers of skin. SCCs may occur on all areas of the body including the mucous membranes, but are most common in areas exposed to the sun.

Although SCCs usually remain confined to the epidermis for some time, they eventually penetrate the underlying tissues if not treated. When this happens, they can be disfiguring. In a small percentage of cases, they spread (metastasize) to distant tissues and organs and can become fatal. SCCs that metastasize most often arise on sites of chronic inflammatory skin conditions or on the mucous membranes or lips.

What Causes It
Chronic exposure to sunlight causes most cases of squamous cell carcinoma. That is why tumors appear most frequently on sun-exposed parts of the body: the face, neck, bald scalp, hands, shoulders, arms, and back. The rim of the ear and the lower lip are especially vulnerable to the development of these cancers.

Squamous cell carcinomas may also occur where skin has suffered certain kinds of injury: burns, scars, long-standing sores, sites previously exposed to X-rays or certain chemicals (such as arsenic and petroleum by-products). In addition, chronic skin inflammation or medical conditions that suppress the immune system over an extended period of time may encourage development of squamous cell carcinoma.

Occasionally, squamous cell carcinoma arises spontaneously on what appears to be normal, healthy, undamaged skin. Some researchers believe that a tendency to develop this cancer may be inherited.

Who Gets It
Anyone with a substantial history of sun exposure can develop squamous cell carcinoma. But people who have fair skin, light hair, and blue, green, or gray eyes are at highest risk. Those whose occupations require long hours outdoors or who spend extensive leisure time in the sun are in particular jeopardy. Dark-skinned individuals of African descent are far less likely than fair-skinned individuals to develop skin cancer.

More than two thirds of the skin cancers that individuals of African descent develop are SCCs, usually arising on the sites of preexisting inflammatory skin conditions or burn injuries. Although dark-skinned individuals of any background are less likely than fair-skinned individuals to develop skin cancer, it is still essential for them to practice sun protection.

Precancerous Conditions
Certain precursor conditions, some of which result from extensive sun damage, are worth noting. They are sometimes associated with the later development of SCC.
They include:
1) Actinic keratoses are rough, scaly, slightly raised growths that range in color from brown to red and may be up to one inch in diameter. They appear most often in older people. Some experts believe that actinic keratosis is the earliest form of SCC.

2) Actinic cheilitis is a type of actinic keratosis occurring on the lips. It causes them to become dry, cracked, scaly, and pale or white. It mainly affects the lower lip, which typically receives more sun exposure than the upper lip.

3) Leukoplakia are white patches or plaques on the tongue or inside of the mouth, arising in the mucous membranes, have the potential to develop into SCC. They are caused by sources of chronic irritation, including smoking or other tobacco use, and rough teeth or rough edges on dentures and fillings. Leukoplakia on the lips are mainly caused by sun damage.

4) Bowen’s disease is generally considered to be a superficial SCC that has not yet spread. It appears as a persistent red–brown, scaly patch which may resemble psoriasis or eczema. If untreated, it may invade deeper structures.

Regardless of appearance, any change in a preexisting skin growth, or the development of a new growth or open sore that fails to heal, should prompt an immediate visit to a physician. If it is a precursor condition, early treatment will prevent it from developing into SCC. Often, all that is needed is a simple surgical procedure or application of a topical chemotherapeutic agent.

Squamous cell carcinomas occur most frequently on areas of the body that have been exposed to the sun for prolonged periods. Usually, the skin in these areas reveals telltale signs of sun damage, such as wrinkling, changes in pigmentation, and loss of elasticity.

Warning Signs of Squamous Cell Carcinoma

A wart-like growth that crusts and occasionally bleeds.

A persistent, scaly red patch with irregular borders that sometimes crusts or bleeds.

An open sore that bleeds and crusts and persists for weeks.

An elevated growth with a central depression that occasionally bleeds. A growth of this type may rapidly increase in size.

A persistent, scaly red patch with irregular borders that sometimes crusts or bleeds.

An open sore that bleeds and crusts and persists for weeks.

Treatment Options
After a physician’s examination, a biopsy will be performed to confirm the diagnosis of SCC. This involves removing a piece of the affected tissue and examining it under a microscope. If tumor cells are present, treatment (usually surgery) is required.

Fortunately, there are several effective ways to eradicate SCC. The choice of treatment is based on the type, size, location, and depth of penetration of the tumor, as well as the patient’s age and general state of health.

Treatment can almost always be performed on an outpatient basis in a physician’s office or at a clinic. A local anesthetic is used during most procedures. Pain or discomfort is usually minimal with most techniques, and there is rarely much pain afterwards.

Curettage and Electrodesiccation
As with AKs, the growth is scraped off with a curette and the tumor site desiccated with an electrocautery needle. But when treating BCCs or SCCs, the procedure is typically repeated a few times to help assure that all cancer cells are eliminated. Local anesthesia is required.

Excisional Surgery
Along with the above procedure, this is one of the most common treatments for BCCs and SCCs. Using a scalpel, the physician removes the entire growth along with a surrounding border of apparently normal skin as a safety margin. The incision is closed, and the growth is sent to the laboratory to verify that all cancerous cells have been removed.

Radiation
X-ray beams are directed at the tumor. Total destruction usually requires several treatments a week for a few weeks. This is ideal for tumors that are hard to manage surgically and for elderly patients who are in poor health.

Cryosurgery
This is the most widely used treatment for individual AKs. It is especially useful when a limited number of lesions are present. Liquid nitrogen is applied to the growths with a cotton-tipped applicator or spray device. This freezes them without requiring any cutting or anesthesia. They subsequently blister or become crusted and fall off. Some temporary redness and swelling can occur. In some patients, pigment may be lost.

Laser Surgery
The skin’s outer layer and variable amounts of deeper skin are removed using a carbon dioxide or erbium YAG laser. Lasers are effective for removing actinic cheilitis from the lips and AKs from the face and scalp. They give the physician good control over the depth of tissue removed, much like chemical peels. Lasers are also used as a secondary therapy when topical medications or other techniques are unsuccessful. However, local anesthesia may be required. The risks of scarring and pigment loss are slightly greater than with other techniques.

Photodynamic Therapy (PDT)
PDT can be especially useful for lesions on the face and scalp. Topical 5-aminolevulinic acid (5-ALA) is applied to the lesions at the physician’s office. As soon as an hour later, those medicated areas can be activated by a strong light. This treatment selectively destroys AKs while causing minimal damage to surrounding normal tissue. Some redness and swelling can result from this newer therapy.

Imiquimod
FDA-approved for the treatment of genital warts, this topical cream is a promising new treatment for actinic keratoses and Bowen's disease. It causes cells to produce interferon, a chemical that attacks cancerous and precancerous cells.