Mayo Clinic Health Manager
Get free personalized health guidance for you and your family.
Get Started
About our e-newsletters
- Free e-newsletters
- Mayo Clinic expertise
- We do not share your e-mail address
Housecall, our weekly general-interest e-newsletter, keeps you up to date on a wide variety of health topics with timely, reliable, practical information, recipes, blogs, questions and answers with Mayo Clinic experts and more. Our biweekly topic-specific e-newsletters also include blogs, questions and answers with Mayo Clinic experts, and other useful information that will help you manage your health.
Housecall Archives
Mayo Clinic Housecall
Stay up to date on the latest health information.
What you get
- Free weekly e-newsletter
- Mayo Clinic expertise
- Recipes, tools and other helpful information
- We do not share your e-mail address
Causes
By Mayo Clinic staff
Your skin consists of three layers — the epidermis, which is closest to the surface, the dermis and the subcutis. Basal cells, which produce new skin cells, are at the bottom or basal layer of the epidermis. Normally, the new cells push older cells toward the skin's surface, where the old cells die and are sloughed off. This process is controlled by DNA, the body's genetic blueprint. But when DNA is damaged — by solar radiation, for example — the process of cell death and renewal no longer occurs as it should. Instead, cells may grow out of control and eventually form a cancerous tumor.
Environmental factors
As with many other diseases, basal cell carcinomas seem to result from a combination of genetic and environmental factors. Most of the environmental damage to skin cells comes from exposure to UV radiation from sunlight. Although some studies show that the greatest harm occurs during childhood and adolescence, UV damage also appears to be cumulative, so the more time you spend in the sun, the greater your chance of developing skin cancer. Your risk increases even more if most of your outdoor exposure takes place in locales or at times of day when the sun is strongest.
Other environmental factors that can lead to basal cell carcinoma include:
- Therapeutic radiation. Psoralen plus ultraviolet A (PUVA) treatments for psoriasis and X-rays to the head or neck increase your risk of basal cell carcinoma as well as of other, more serious forms 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 basal 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.
- Immunosupressant drugs. People who take medications to prevent organ rejection after transplant surgery have a greatly increased risk of basal cell carcinoma, though symptoms may not appear for years after the operation.
Genetic factors
Several inherited disorders cause basal cell carcinoma or greatly increase your risk, including:
- Nevoid basal cell carcinoma syndrome (Gorlin's syndrome). People with this rare genetic disorder have numerous basal cell carcinomas as well as pitting on their hands and feet, spine abnormalities, and cataracts.
- Bazex's syndrome. This disorder is marked by numerous basal cell tumors on the face and by a lack of sweating and body hair.
- Xeroderma pigmentosum. People with xeroderma pigmentosum, which causes an extreme sensitivity to sunlight, are at high risk of skin cancer because they have little or no ability to repair damage to the skin from ultraviolet light.
- Wood GS, et al. Nonmelanoma skin cancers: Basal cell and squamous cell carcinomas. In: Abeloff MD, et al. Abeloff's Clinical Oncology. 4th ed. Philadelphia, Pa.: Churchill Livingstone; 2008. http://www.mdconsult.com/das/book/body/119479231-3/0/1709/83.html?tocnode=55017273&fromURL=83.html#4-u1.0-B978-0-443-06694-8..50078-6--cesec29_2759. Accessed Feb. 6, 2009.
- Basal cell carcinoma. American Academy of Dermatology. http://www.aad.org/public/publications/pamphlets/sun_basal.html. Accessed Feb. 6, 2009.
- Detailed guide: Skin cancer - basal and squamous cell. American Cancer Society. http://www.cancer.org/docroot/CRI/content/CRI_2_4_1X_What_is_skin_cancer_51.asp. Accessed Feb. 6, 2009.
- Urist MM, et al. Melanoma and cutaneous malignancies. In: Townsend CM, et al. Townsend: Sabiston Textbook of Surgery. 18th ed. Philadelphia, Pa.: W.B. Saunders; 2007.http://www.mdconsult.com/das/book/body/119479231-5/0/1565/1.html?tocnode=54736195&fromURL=1.html#4-u1.0-B978-1-4160-3675-3..X5001-1--TOP_1. Accessed Feb. 6, 2009.
- Burns J. Bartter's syndrome and basal cell carcinoma. In: Ferri FF. Ferri's Clinical Advisor 2009. St. Louis, Mo.: Mosby; 2008. http://www.mdconsult.com/das/book/body/119515236-9/801847095/1701/79.html#4-u1.0-B978-0-323-04134-8..50005-7--cesec92_1598. Accessed Feb. 9, 2009.
- Sunscreen. The Skin Cancer Foundation. http://www.skincancer.org/the-scfs-guide-to-sunscreens.html. Accessed Feb. 6, 2009.
- Basal cell carcinoma of the skin. National Cancer Institute. http://www.cancer.gov/cancertopics/pdq/treatment/skin/HealthProfessional/page5. Accessed Feb. 6, 2009.
- Ridky TW. Nonmelanoma skin cancer. Journal of the American Academy of Dermatology. 2007;57:484.
- Neoplasia. In: Kumar V, et al. Robbins and Cotran's Pathologic Basis of Disease. 7th ed. Philadelphia, Pa.: Saunders Elsevier; 2005. http://www.mdconsult.com/das/book/body/119515236-4/801835407/1249/66.html#4-u1.0-B0-7216-0187-1..50011-0--cesec92_600. Accessed Feb. 6, 2009.
- Arsenic toxicity exposure pathways. U.S. Department of Health and Human Services. http://www.atsdr.cdc.gov/csem/arsenic/exposure_pathways.html. Accessed Feb. 6, 2009.
- Common questions about diet and cancer. American Cancer Society. http://www.cancer.org/docroot/PED/content/PED_3_2X_Common_Questions_About_Diet_and_Cancer.asp?sitearea=PED. Accessed Feb. 6, 2009.
- Food Groups to Encourage. In: U.S. Department of Health and Human Services and U.S. Department of Agriculture. Dietary Guidelines for Americans. 6th Edition. Washington, D.C.: U.S. Government Printing Office; 2005. http://www.health.gov/DietaryGuidelines/dga2005/document/html/chapter5.htm. Accessed Feb 6, 2009.
- Premalignant and malignant nonmelanoma skin tumors. In: Habif TP. Clinical Dermatology: A Color Guide to Diagnosis and Therapy. 4th ed. New York, N.Y.: Mosby; 2004. http://www.mdconsult.com/das/book/body/119515236-5/0/1195/157.html?tocnode=51442435&fromURL=157.html#4-u1.0-B0-323-01319-8..50023-6_2588. Accessed Feb. 6, 2009.
