Squamous cells are small, flat skin cells normally found in the outermost layer of skin, called the epidermis. When squamous cells become cancerous (malignant), they typically develop into nodular or flat skin tumors, sometimes with a surrounding area of inflammation.

Most cases of squamous cell carcinoma are caused by unprotected, long-term exposure to the sun's ultraviolet rays. They usually occur on the sun-exposed skin of people who have spent a great deal of time outdoors, especially those with fair complexions and blue eyes. Occasionally, cancer develops within a scaly patch of sun-damaged skin called an actinic keratosis, which has a white, pink, yellow or brownish tint.

Although most cases of squamous cell carcinoma are related to sun exposure, a smaller number develop in skin that has been injured or exposed to carcinogens (cancer-causing agents). Common locations for this type of squamous cell cancer include:

• Scars, burns, chronic (long-lasting) ulcers and other areas of skin injury
• The legs and torso in workers exposed to arsenic or to industrial hydrocarbons, such as tar, soot, crude paraffin, anthracene or pitch
• Areas of the genitals affected by genital warts
• Areas of psoriasis treated with PUVA therapy, a combination of a light-sensitizing agent called psoralen and plus ultraviolet light

Most squamous cell carcinomas that are detected early cause only a localized area of skin damage, usually on a sun-exposed portion of the head or hand. Depending upon the location, however, there can be disfiguring scarring if these skin cancers are not caught early and excised while they are small. In a small percentage of cases, the cancer is more aggressive and spreads (metastasizes) to the lymph nodes and other parts of the body. Squamous cell carcinoma is most likely to spread when it is on the lips, ears, penis, scrotum or vulva.

Squamous cell carcinoma is the second most common skin cancer in the United States, with more than 200,000 cases each year. Since the early 1980s, the number of cases has risen dramatically, increasing at a rate of about 10% per year. People with weakened immune defenses are at especially high risk of developing squamous cell cancer. This includes people who are HIV positive, have received transplants or are taking immune-suppressing medications.

Squamous cell skin carcinoma usually appears as a tiny, painless nodule or patch that sometimes, but not always, is surrounded by an area of inflammation. The surface of the cancer can be scaly, crusted or wartlike, and its center can form an open sore.

Although squamous cell carcinoma can develop on almost any part of the body, including the genitals and the soles of the feet, the most common locations are the head (scalp, lips, ears, inside the mouth), legs, or the back of the hands or on the arms.

Your doctor will examine your skin and may shave away (excise) a small piece of abnormal skin to be examined in a laboratory. This procedure is called a biopsy. Occasionally, the doctor will remove the entire abnormal area and send it to a laboratory to be examined under a microscope.

In the laboratory, a pathologist will examine the biopsy specimen and determine if the specimen is a skin cancer. If so, the pathologist will examine the margins (borders) of the specimen to determine if the skin cancer has been removed by the biopsy. If any cancer cells remain at the margin, another procedure will be necessary to remove any remaining skin cancer cells.

Once squamous cell carcinoma develops on the skin, it usually grows slowly. In general, if a squamous cell carcinoma is neglected and allowed to reach a diameter of more than 2 centimeters (about three-quarters of an inch), it is three times more likely to spread than a smaller cancer.

Because squamous cell carcinoma is caused by unprotected exposure to sunlight, you can take several steps to help to prevent this cancer:

• Apply a sunscreen before you go outdoors. Choose a sunscreen that has a sun protection factor (SPF) of 15 or above, with a broad spectrum of protection against both ultraviolet A and ultraviolet B rays.
• Use a sunblock on your lips. Choose a product that has been formulated for the lips, with an SPF of 20 or more.
• Limit your time outdoors when the sun is at its peak. In most parts of the continental United States, this is between about 10 a.m. to 3 p.m.
• Wear sunglasses with ultraviolet light protection.
• Wear long pants, a shirt with long sleeves and a hat with a wide brim.
• Become aware of drugs and skin-care products that can increase your skin's risk of ultraviolet damage. These include certain antibiotics and drugs used to treat psychiatric illness, high blood pressure, heart failure, acne and allergies.

If you are taking prescription medications, and you spend significant time outdoors, ask your doctor if you need to take precautions to avoid sun exposure. Also, be aware that certain nonprescription skin-care products contain chemicals called alpha-hydroxy acids that can make your skin more vulnerable to damage from sunlight.

If a squamous cell carcinoma develops on your skin, you can limit the area of damage by detecting the problem early. To do this, examine your entire skin surface thoroughly every one to two months. Use a mirror to check for skin abnormalities on less visible areas of your back, shoulders, upper arms, buttocks and the soles of your feet.

There are many surgical and nonsurgical ways to treat squamous cell carcinoma that has not spread. These include:

• Excision. All visible cancer is cut away together with a 3-millimeter to 10-millimeter margin of healthy tissue, then the skin is stitched closed with sutures. If a large area of skin is removed, a skin graft may be necessary.



• Curettage and electrodesiccation. All visible cancer is scraped away, then an electric probe is used to kill any remaining microscopic cancerous cells.



• Cryosurgery. The cancerous cells are killed by freezing them with liquid nitrogen. This treatment usually is reserved for precancers or very small tumors.



• Radiation. The cancer is destroyed with high-energy rays aimed from outside the body.



• Moh's micrographic surgery. The tumor is shaved away in thin layers and one layer at a time is checked under the microscope to preserve as much healthy skin as possible while making sure that all of the cancer is removed. This is the most common treatment for squamous cell cancers on the eyelids, nose, fingers and other areas.



• Other treatments. These include topical 5-fluorouracil (Efudex, Fluoroplex), an anticancer drug applied directly to the skin; laser therapy (using a narrow laser beam to destroy the cancer); and interferon alfa injected directly into the tumor.

Which treatment is best for you depends on many factors, including the size and location of the cancer, whether it has returned after previous treatment, your age and your general health. Once your treatment is finished and your cancer is gone, your doctor will schedule follow-up skin examinations for you at regular intervals, such as every three months for the first year, and then less often after that.

Call your primary care doctor or a dermatologist (a doctor who specializes in skin problems) if you notice that you have an abnormal nodule or patch anywhere on your skin, or if you have a skin ulcer that does not heal.

In most cases, the outlook is excellent. Overall, 95% to 98% of squamous cell carcinomas can be cured if they are treated early and have not spread. Once a squamous cell carcinoma has spread, the 5-year survival rate is less than 50%, even with aggressive cancer therapy.

National Cancer Institute (NCI)
U.S. National Institutes of Health
Public Inquiries Office
6116 Executive Blvd.
Room 3036A
Bethesda, MD 20892-8322
Phone: 301-435-3848
Toll-Free: 1-800-422-6237
TTY: 1-800-332-8615
Email: cancergovstaff@mail.nih.gov
http://www.nci.nih.gov/

American Cancer Society (ACS)
Toll-Free: 1-800-227-2345
TTY: 1-866-228-4327
http://www.cancer.org/

American Academy of Dermatology
P.O. Box 4014
Schaumburg, IL 60168-4014
Phone: 847-240-1280
Toll-Free: 1-888-462-7546
Fax: 847-240-1859
http://www.aad.org/

The Skin Cancer Foundation
149 Madison Ave.
Suite 901
New York, NY 10016
Phone: 212-725-5176
Email: info@skincancer.org
http://www.skincancer.org/