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Squamous Cell Carcinoma

Definition :
In November 2006, first lady Laura Bush had a small squamous cell carcinoma removed from her shin. Though hers was a high-profile case, it was by no means unique. An estimated 250,000 new cases of squamous cell carcinoma are diagnosed in the United States every year. And though squamous cell carcinoma was once found mainly in older adults, it's occurring with increasing frequency in people younger than 40.

Mrs. Bush's cancer was caught and treated early. In such cases, squamous cell carcinoma is highly curable and rarely causes further problems. But untreated squamous cell carcinoma can destroy healthy tissue around the tumor, spread to the lymph nodes or other organs, and occasionally prove fatal.

Most squamous cell carcinomas result from prolonged exposure to ultraviolet (UV) radiation, either from sunlight or from tanning beds or lamps. Avoiding UV light as much as possible is the best protection. Sunscreen is an important part of a sun-safety program, but by itself doesn't completely prevent squamous cell carcinoma or other types of skin cancer.

Causes :
Your skin consists of three layers — the epidermis, dermis and subcutis. The epidermis, the topmost layer, is as thin as a pencil line and provides a protective layer of skin cells that your body continually sheds. Squamous cells lie just below the outer surface. Under a microscope, squamous cells in the deeper part of the epidermis resemble bricks; closer to the surface, they
look like fish scales.

Basal cells, which produce new skin cells, are at the bottom of the epidermis. Squamous cell carcinomas develop from cells just above the basal layer. They form when cell death and renewal no longer occur as they should. Ordinarily, new cells push older cells toward the skin's surface, and the older cells die and are sloughed off — a process controlled by DNA, the body's genetic material. But if DNA is damaged, this orderly pattern is disrupted, causing cells to grow out of control.

The DNA-UV connection
Most of the damage to DNA in skin cells results from exposure to UV radiation from sunlight and commercial tanning lamps and beds. The damage is cumulative, so the more time you spend in the sun or in a tanning booth, the greater your chance of developing skin cancer. Your risk increases even more if most of your outdoor exposure occurs at times of the day or in locations where the sun is strongest.

Although sun exposure causes most cases of squamous cell cancinoma, other factors can also lead to this type of cancer, including :

  • Therapeutic radiation. Psoralen UVA (PUVA) treatments for psoriasis and X-rays to the head or neck increase your risk of squamous cell carcinoma as well as of melanoma, the most deadly form of skin cancer. It can take years for skin cancers to develop, and many radiation-induced carcinomas that occur later in life may have had their origins in radiation treatments for childhood acne or ringworm. The likelihood that therapeutic radiation will cause cancer depends on a number of factors, including the pigmentation in your skin, the total dose of radiation you receive, and your medical status.
  • Chemical toxins. Arsenic, a toxic metal that's found widely in the environment, is a well-known cause of squamous cell carcinoma and other cancers. Though arsenic contaminates the soil, air and groundwater, most people get their greatest exposure in food, especially chicken, beef and fish, and in wine grapes sprayed with arsenic-containing toxins. The U.S. Department of Health and Human Services estimates that the average American ingests 11 to 14 milligrams of arsenic every day. Farmers, refinery workers, and people who drink contaminated well water or live near smelting plants are likely to ingest much higher levels.
  • Human papilloma-virus (HPV). This group of viruses has more than 100 strains, about a third of which are sexually transmitted. Some of the viruses cause genital warts; others can lead to cancer of the vagina, cervix or penis. Now, researchers think that infection with certain types of HPV may also play a role in the development of squamous cell skin cancers.
  • Immunosupressant drugs. Up to 80 percent of people who take medications to prevent organ rejection after transplant surgery develop squamous cell carcinoma, though symptoms may not appear for years after surgery. People who have had heart transplants are at greatest risk because they tend to take more drugs at higher doses than do people who have other types of transplants.

Risk Factor :
A lifetime spent in the sun — or in commercial tanning booths — is the most common cause of squamous cell carcinoma. The threat is greater if you live in a sunny or high-altitude location, both of which expose you to more UV radiation. The risk is also greater if most of your exposure occurred when you were young or you inherit a sensitivity that causes your DNA to sustain more damage than usual from UV light.

Other factors that can contribute to squamous cell carcinoma include :

  • Fair skin. If you have very light skin or freckle or sunburn easily, you're more likely to develop skin cancer than is someone with a darker complexion. Fair-skinned people of Northern European ancestry are particularly at risk. Queensland, Australia, has the highest skin cancer rate in the world because it has unusually high levels of UV radiation and because most of its inhabitants have sensitive English or Irish complexions.
  • Your sex. Men are far more likely to develop squamous cell carcinoma than women are, probably because of their greater exposure to the sun.
  • A personal history of skin cancer. If you've had squamous cell carcinoma once, you're much more likely to develop it again.
  • Weakened immune system. People with weakened immune systems are at greater risk of many diseases, including skin cancer. This includes people who have chronic leukemias, other cancers or HIV/AIDS, and those who have undergone organ transplants or who are, for other reasons, taking medications that suppress the immune system.
  • Rare genetic disorder. People with xeroderma pigmentosum, which causes an extreme sensitivity to sunlight, have a greatly increased risk of developing skin cancer because they have little or no ability to repair damage to the skin from ultraviolet light.
  • Smoking. Smoking increases your risk of squamous cell carcinoma, and the risk is directly proportional to the number of cigarettes smoked. Although researchers aren't sure why smoking has this effect, they theorize that tobacco damages DNA, making cancerous changes in cells more likely.
  • Skin inflammation or injury. You have a slightly higher chance of developing squamous cell carcinoma if you have a large scar, skin infection or an inflammatory skin disease, such as psoriasis.

When to seek medical advice :
Squamous cell carcinomas may be difficult to distinguish from normal skin, especially in the early stages. Yet the sooner they're diagnosed and treated, the better the outcome. See your dermatologist if you have a sore or scab that doesn't heal in about two weeks or a flat patch of scaly skin that won't go away.

Symptoms :
Although squamous cell carcinomas usually develop on sun-exposed skin, they can occur anywhere on your body, including inside your mouth and anus, and on the genitals in both men and women. The appearance of the tumors can vary, but the most common forms include :
  • A firm, red nodule on your face, lower lip, ears, neck, hands or arms
  • A flat lesion with a scaly crust on your face, ears, neck, hands or arms
  • A new ulceration or raised area on a pre-existing scar or ulcer
  • An ulcer or flat, white patch inside your mouth
  • A red, raised patch or ulcerated sore in the anus or on your genitals

Squamous cell carcinomas are usually slow growing and can be difficult to spot, especially when they appear on skin that has other signs of sun damage, such as changes in pigmentation, loss of elasticity and wrinkling. They can also be mistaken for actinic keratoses — rough, scaly, dark brown or pink patches that appear after years of sun exposure. A small number of actinic keratoses eventually develop into squamous cell carcinomas.

In addition to taking a complete medical history and checking the affected area of skin, your doctor may remove a small skin sample (biopsy) for examination under a microscope. Often, the biopsy is sent to a pathologist who has special expertise in diagnosing skin samples.

A suspected squamous cell carcinoma is often biopsied by shaving off the top layers of skin with a surgical blade. Tumors that have spread deeper into the skin may be partially or completely removed (incisional or excisional biopsy). Because all biopsies are likely to leave a small scar, talk to your doctor about the types of biopsies and their potential for scarring before having the procedure.

Complications :
When treated early, squamous cell carcinomas generally cause no problems. Untreated tumors can spread to nearby lymph nodes or to other organs, though this is uncommon. People who have had organ transplants or have chronic lymphocytic leukemia or HIV/AIDS are far more likely to have an aggressive form of squamous cell carcinoma than are people who are otherwise healthy.

Tumors on the lips and ears more often spread to other sites or recur after treatment. Large tumors — those measuring 2 centimeters (about 3/4 inch) or more — are also more likely to spread than smaller tumors are.

Most squamous cell carcinomas can be completely removed with relatively minor surgery or occasionally with a topical medication. The type of squamous cell carcinoma treatment usually depends on the size, location and aggressiveness of the tumor and may include one or more of the following :
  • Freezing. This involves removing cancerous cells by freezing them with liquid nitrogen (cryosurgery). It's effective for small squamous cell carcinomas, but isn't recommended for larger tumors or those on your nose, ears or eyelids.
  • Simple excision. In this procedure, your doctor cuts out the cancerous tissue and a surrounding margin of healthy skin. Your doctor may recommend a wide excision — removing additional normal skin around the tumor — in some cases. To minimize scarring, especially on your face, consult a doctor skilled in skin reconstruction.
  • Laser therapy. An intense beam of light vaporizes growths, usually with little damage to surrounding tissue and with a reduced risk of bleeding, swelling and scarring. Lasers are often used to treat superficial carcinomas on the lips.
  • Mohs' surgery. This is often considered the most effective treatment for squamous cell carcinomas, especially those that are larger than 2 centimeters, have recurred, or are located on the face, mucous membranes or genital area. During the procedure, your doctor removes the tumor layer by layer, examining each layer under the microscope until no abnormal cells remain. This allows the entire growth to be removed without taking an excessive amount of surrounding healthy skin. Because it requires particular expertise, Mohs' surgery should only be performed by doctors specifically trained in the procedure.
  • Radiation therapy. This may be an option for treating large cancers on the eyelids, lips and ears — areas that are difficult to treat surgically — or for tumors too deep to cut out. The recurrence rate is high, however — as much as 50 percent for large tumors.
  • Chemotherapy. For very superficial cancers, creams or lotions containing anti-cancer agents may be applied directly to your skin. Some of these medications can cause severe inflammation and scarring, so be sure to discuss potential complications with your doctor.

Most squamous cell carcinomas can be prevented. To protect yourself :

  • Avoid the midday sun. Sunlight is strongest between 10 a.m. and 4 p.m., so try to schedule outdoor activities for other times of the day, even in winter or when it's cloudy. You absorb UV radiation year-round, and clouds offer little protection from damaging rays. Keep in mind that sunlight is more intense when it reflects off water, sand and snow.
  • Use sunscreen year-round. Sunscreens don't filter out all harmful UV radiation, but they play a major role in an overall sun protection program. Wear a broad-spectrum sunscreen with a sun protection factor (SPF) of at least 15 when you go outside, year-round. Use about 1 ounce — the amount that fits in the palm of your hand — to cover your entire body, including your lips, ears and the backs of your hands and neck. Apply sunscreen 20 to 30 minutes before sun exposure and reapply it every two hours throughout the day as well as after swimming or exercising.

    A sunscreen called Anthelios SX, which has been widely used in Europe, is now available in the United States. It offers better protection from UVA rays than do traditional broad-spectrum sunscreens and may be more effective in preventing skin cancer.

    Still, don't rely on any sunscreen as your sole means of sun protection. UVA rays penetrate the skin more deeply than UVB rays do and are responsible for skin aging as well as for increasing your risk of cancer.

  • Wear protective clothing. Because no sunscreen provides complete protection, it's important to also wear tightly woven clothing that covers your arms and legs and a broad-brimmed hat rather than a baseball cap or visor. Some companies sell photoprotective clothing. Your dermatologist can recommend an appropriate brand. And don't forget sunglasses. Look for those that provide full protection from both UVA and UVB rays.
  • Avoid tanning beds. Some tanning salon operators claim that indoor tanning is less damaging than natural sunlight, but the opposite may be true. Tanning beds emit UVA rays, which penetrate deeper into your skin and are more likely to cause cancerous lesions. Some researchers attribute the unusual increase in skin cancers among younger people to the use of tanning beds and sun lamps. If you can't resist the sun-kissed look, choose self-tanning lotions or sprays.
  • Be aware of sun-sensitizing medications. Some common prescription and over-the-counter drugs make your skin more sensitive to sunlight. These include antibiotics; certain cholesterol, high blood pressure and diabetes medications; ibuprofen (Advil, Motrin, others); and the acne medication isotretinoin (Accutane). Ask your druggist about the side effects of any medications you take. If they make you more sun sensitive, take extra precautions.
  • Perform regular skin checks. Examine your skin often for new growths or changes in existing moles, freckles, bumps and birthmarks. Don't forget to check your scalp, ears, genital area and buttocks.
  • Get enough vitamin D. This vitamin may help lower the risk of certain cancers. Although it's normally produced by sunlight on your skin, many experts recommend getting your daily requirement of vitamin D through food or supplements.
  • Go green. Australian researchers report that eating green leafy vegetables, especially spinach, may help reduce the risk of skin cancer, particularly among people who have had the disease before. The benefits likely come from the wide range of nutrients and antioxidants found in vegetables, but health officials are quick to point out that avoiding daily sun exposure, using sunscreen and wearing protective clothing are still the best ways to prevent skin cancer.
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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