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Causes
By Mayo Clinic staff
Squamous cells lie just below the outer surface of your skin. Squamous cell carcinomas develop when cell death and renewal no longer occur as they should. Ordinarily, new cells push older cells toward your skin's surface, and the older cells die and are sloughed off — a process controlled by DNA, your 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 when the sun is strongest.
Although sun exposure causes most cases of squamous cell cancinoma, other factors also can lead to this type of cancer, including:
- Therapeutic radiation. Psoralen plus ultraviolet A (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 radiation-induced carcinomas can occur later in life due to 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 and the total dose of radiation you receive.
- 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 seafood, rice, mushrooms and chicken. Farmers, refinery workers, and people who drink contaminated well water or live near smelting plants are likely to ingest higher levels of arsenic.
- Human papillomavirus (HPV). This group of viruses has more than 100 strains, many 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.
- Immunosuppressant drugs. Many people who take medications to prevent organ rejection after transplant surgery develop squamous cell carcinoma, though symptoms may not appear for years after transplantation. People who have had heart transplants are at greatest risk because they tend to take more immune-suppressing drugs at higher doses than do people who have other types of transplants.
- Squamous cell carcinoma. The Skin Cancer Foundation. http://www.skincancer.org/squamous-cell-carcinoma.html. Accessed Feb. 17, 2011.
- Detailed guide: Skin cancer — basal and squamous cell. American Cancer Society. http://www.cancer.org/acs/groups/cid/documents/webcontent/003139-pdf.pdf. Accessed Feb. 17, 2011.
- Lim JL. Epidemiology and clinical features of cutaneous squamous cell carcinoma. http://www.uptodate.com/home/index.html. Accessed Feb. 17, 2011.
- Public health statement for arsenic. Agency for Toxic Substances and Disease Registry. U.S. Centers for Disease Control and Prevention. http://www.atsdr.cdc.gov/PHS/PHS.asp?id=18&tid=3. Accessed Feb. 18, 2011.
- Skin cancer treatment PDQ: Professional version. National Cancer Institute. http://www.cancer.gov/cancertopics/pdq/treatment/skin/HealthProfessional/AllPages/Print. Accessed Feb. 17, 2011.
- Common medications may increase sun sensitivity. The Skin Cancer Foundation. http://www.skincancer.org/common-medications-may-increase-sun-sensitivity.html. Accessed Feb. 18, 2011.
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