What Is It?
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 small, 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 actinic keratosis, which has a 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
- The lips, mouth and larynx in smokers, where cancer growth is triggered by the carcinogens in tobacco
Most squamous cell carcinomas cause only a limited, localized area of skin damage, usually on a sun-exposed portion of the head or hand. In a small percent of cases, however, 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 percent 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 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) or the back of the hands or arms.
Your doctor will examine your skin and may shave away (excise) only 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 assign a grade for the cancer, based on the number of abnormal cells and their appearance. The cancer also can be staged based on how deeply it has invaded the skin and how far it has spread. In general, the higher the grade or stage of a squamous cell carcinoma, the more likely it is to spread. For that reason, if your cancer is assigned a high grade or stage, further tests are needed to see if the cancer has spread to your lymph nodes or other areas.
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.
To help prevent squamous cell carcinoma of the lips and mouth, avoid using cigarettes, pipes, cigars and chewing tobacco (smokeless tobacco). 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- 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 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 in order 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.
When To Call A Professional
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. If you develop an abnormal spot inside your mouth that does not heal in two weeks, consult your dentist as soon as possible, especially if you have a history of using tobacco products.
In most cases, the outlook is excellent. Overall, 95 percent to 98 percent of squamous cell carcinomas can be cured if they are treated early and have not spread. This is especially true for cancers that are located on sun-exposed skin surfaces, where the risk of the cancer spreading generally is rather low. Once a squamous cell carcinoma has spread, the five-year survival rate is less than 50 percent, even with aggressive cancer therapy.
Diseases and Conditions Center
All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.