Squamous cell carcinoma is the second most common type of skin cancer, after basal cell carcinoma. Each year, at least 200,000 Americans are diagnosed with squamous cell carcinoma.
People who develop squamous cell carcinoma are usually those who have had regular exposure to sunlight. Squamous cell carcinoma used to be primarily a disease of older men who had spent many years working outdoors. However, increasing numbers of young people and women are developing this type of skin cancer, presumably reflecting increased their exposure to the sun during leisure time.
Squamous cell carcinoma begins in the upper part of the epidermis, the uppermost layer of the skin, and grows slowly. Most squamous cell carcinomas can be treated successfully if detected early. However, if they are ignored, they can spread. They tend to be more aggressive than basal cell carcinomas. They are more likely than basal cell carcinomas to spread to the fatty tissue right under the skin. They are also more likely than basal cell carcinomas to spread to lymph nodes and to metastasize (spread to distant parts of the body), but it is still quite unusual for this to happen.
Who Is at Risk?
People who have light-colored skin, red or blond hair, and blue, green, or gray eyes have a higher risk of squamous cell carcinoma than people with darker pigmentation do. Sun exposure is a key risk factor. Squamous cell carcinoma develops most often on parts of the body that are frequently exposed to the sun; these areas include the face, lips, ears, and neck and the backs of the hands. Actinic keratosis (a type of precancerous skin problem) can sometimes develop into squamous cell carcinoma. Squamous cell carcinomas can also occur in places where the skin has been damaged, even on parts of the body that are not exposed to the sun. These areas include burns, scars, persistent sores, and sites that have been exposed to x-rays, arsenic, or certain petroleum byproducts. Conditions that suppress the body's immune defenses, such as HIV infection or the prolonged use of immunosuppressive drugs, may also promote the development of squamous cell carcinoma.
Diagnosing Squamous Cell Carcinoma
A squamous cell carcinoma can appear as a bleeding or non-healing sore, a reddish patch, or a raised growth that resembles a wart. Other types of skin cancer and other skin problems may have similar appearances. An examination by a physician is necessary to determine which kind of skin disease is present. If the doctor suspects squamous cell carcinoma, a procedure called a biopsy will be performed, in which a sample of the abnormal area is collected and sent to a laboratory for examination.