A mole (nevus) is a pigmented (colored) spot on the outer layer of the skin (epidermis).
Moles can be round, oval, flat, or raised. They can occur singly or in clusters on any part of the body. Most moles are brown, but colors can range from pinkish flesh tones to yellow, dark blue, or black.
Everyone has at least a few moles. They generally appear by the time a person is 20 and resemble freckles at first. A mole's color and shape don't usually change. Changes in hormone levels that occur during puberty
can make moles larger and darker. New moles may also appear during this period.
A mole usually lasts about 50 years before beginning to fade. Some moles disappear completely, and some never lighten at all. Some moles develop stalks that raise them above the skin's surface; these moles eventually drop off.
Types of moles
About 1-3% of all babies have one or more moles when they are born. Moles that are present at birth are called congenital nevi.
Other types of moles include:
- Junctional moles, which are usually brown and may be flat or slightly raised.
- Compound moles, which are slightly raised, range in color from tan to dark brown, and involve pigment-producing cells (melanocytes) in both the upper and lower layers of the skin (epidermis and dermis).
- Dermal moles, which range from flesh-color to brown, are elevated, most common on the upper body, and may contain hairs.
- Sebaceous moles, which are produced by over-active oil glands and are yellow and rough-textured.
- Blue moles, which are slightly raised, colored by pigment deep within the skin, and most common on the head, neck, and arms of women.
Most moles are benign, but atypical moles (dysplastic nevi) may develop into malignant melanoma
, a potentially fatal form of skin cancer
. Atypical moles are usually hereditary. Most are bigger than a pencil eraser, and the shape and pigmentation are irregular.
Congenital nevi are more apt to become cancerous than moles that develop after birth, especially if they are more than eight inches in diameter. Lentigo maligna (melanotic freckle of Hutchinson), most common on the face and after the age of 50, first appears as a flat spot containing two or more shades of tan. It gradually becomes larger and darker. One in three of these moles develop into a form of skin cancer known as lentigo maligna melanoma.
Causes and symptoms
The cause of moles is unknown, although atypical moles seem to run in families and result from exposure to sunlight.
In the past several years, researchers have identified two genes known as CDKN2A and CDK4 that govern susceptibility to melanoma in humans. Other susceptibility genes are being sought as of early 2003. Most experts, however, think that these susceptibility genes are not sufficient by themselves to account for moles becoming cancerous but are influenced by a combination of other inherited traits and environmental factors.
Only a small percentage of moles require medical attention. A mole that has the following symptoms should be evaluated by a dermatologist (a physician spealizing in skin diseases).
- Appears after the age of 20
- Looks unusual or changes in any way.
A doctor who suspects skin cancer will remove all or part of the mole for microscopic examination. This procedure, which is usually performed in a doctor's office, is simple, relatively painless, and does not take more than a few minutes. It does leave a scar.
The doctor may also use a dermatoscope to examine the mole prior to removal. The dermatoscope, which can be used to distinguish between benign moles and melanomas, is an instrument that resembles an ophthalmoscope. An immersion oil is first applied to the mole to make the outer layers of skin transparent.
A combination of high-frequency ultrasound and color Doppler studies has also been shown to have a high degree of accuracy in distinguishing between melanomas and benign moles.
If laboratory analysis confirms that a mole is cancerous, the dermatologist will remove the rest of the mole. Patients should realize that slicing off a section of a malignant mole will not cause the cancer to spread.
Removing a mole for cosmetic reasons involves numbing the area and using scissors or a scalpel to remove the elevated portion. The patient is left with a flat mole the same color as the original growth. Cutting out parts of the mole above and beneath the surface of the skin can leave a scar more noticeable than the mole.
Scissors or a razor can be used to temporarily remove hair from a mole. Permanent hair removal, however, requires electrolysis or surgical removal of the mole.
Moles are rarely cancerous and, once removed, unlikely to recur. A dermatologist should be consulted if a mole reappears after being removed.
Wearing a sunscreen and limiting sun exposure may prevent some moles. Anyone who has moles should examine them every month and see a dermatologist if changes in size, shape, color, or texture occur or if new moles appear.
A team of researchers at Duke University reported in 2003 that topical application of a combination of 15% vitamin C and 1% vitamin E over a four-day period offered significant protection against sunburn
. The researchers suggest that this combination may protect skin against aging
caused by sunlight as well.
Anyone with a family history of melanoma should see a dermatologist for an annual skin examination. Everyone should know the ABCDEs of melanoma:
- A: Asymmetry, which occurs when the two halves of the mole are not identical
- B: Borders that are irregular or indistinct
- C: Color that varies in a single mole
- D: Diameter, which should be no larger than a pencil eraser (about 6 mm)
- E: Elevated above the surrounding tissue.
— The branch of medicine that studies and treats disorders of the skin.
— A potentially fatal form of skin cancer that develops from melanocytes, which are skin cells containing melanin.
— A dark insoluble pigment found in humans in the skin, hair, choroid layer of the eye, and a part of the brain called the substantia nigra.
Nevus (plural, nevi)
— The medical term for any anomaly of the skin that is present at birth, including moles and birthmarks.
A mole with any of these characteristics should be evaluated by a dermatologist.
Advances in photographic technique have now made it easier to track the development of moles with the help of whole-body photographs. A growing number of hospitals are offering these photographs as part of outpatient mole-monitoring services.
Beers, Mark H., MD, and Robert Berkow, MD, editors. "Dermatologic Disorders: Malignant Tumors." Section 10, Chapter 126. In The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 2004.
Beers, Mark H., MD, and Robert Berkow, MD, editors. "Dermatologic Disorders: Moles." Section 10, Chapter 125. In The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 2004.
Beers, Mark H., MD, and Robert Berkow, MD, editors. "Dermatologic Disorders: Reactions to Sunlight." Section 10, Chapter 119. In The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 2004.
Bennett, D. C. "Human Melanocyte Senescence and Melanoma Susceptibility Genes." Oncogene 22 (May 19, 2003): 3063-3069.
Bessoud, B., N. Lassau, S. Koscielny, et al. "High-Frequency Sonography and Color Doppler in the Management of Pigmented Skin Lesions." Ultra sound in Medicine & Biology 6 (June 2003): 875-879.
Bray, C. "The Development of an Improved Method of Photography for Mole-Monitoring at the University Hospital of North Durham." Journal of Audiovisual Media in Medicine 26 (June 2003): 60-66.
Hall, Daniel J., MD, and Michael Holtel, MD. "Malignant Melanoma of the Face and Neck." eMedicine July 3, 2003. 〈http://www.emedecine.com.ent/topic27.htm〉.
Lin, J. Y., M. A. Selim, C. R. Shea, et al. "UV Photoprotection by Combination Topical Antioxidants Vitamin C and Vitamin E." Journal of the American Academy of Dermatology 48 (June 2003): 866-874.
Tucker, M. A., and A. M. Goldstein. "Melanoma Etiology: Where Are We?" Oncogene 22 (May 19, 2003): 3042-3052.
American Academy of Dermatology. 930 N. Meacham Road, P.O. Box 4014, Schaumburg, IL 60168-4014. (847) 330-0230. Fax: (847) 330-0050. http://www.aad.org.
American Cancer Society. 1599 Clifton Road NE, Atlanta, GA 30329. (800) ACS-2345.
National Cancer Institute (NCI). NCI Public Inquiries Office, Suite 3036A, 6116 Executive Boulevard, MSC8332, Bethesda, MD 20892-8322. (800) 4-CANCER or (800) 332-8615 (TTY). http://www.nci.nih.gov.
Nevus Outreach, Inc. 1601 Madison Blvd., Bartesville, OK 74006. (877) 426-3887. http://www.nevus.org.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.