Definition

A mole (nevus) is a pigmented (colored) spot on the outer layer of the skin (epidermis).

  Description

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 look, at first, like freckles. A mole's color and shape don't usually change. Changes in hormone levels that occur during puberty and pregnancy 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.

  Diagnosis

Only a small percentage of moles require medical attention. A mole that has the following symptoms should be evaluated by a dermatologist (a physician specializing in skin diseases).

• Appears after the age of 20
• Bleeds
• Itches
• 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 doesn't take more than a few minutes. It does leave a scar.

  Treatment

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 requires electrolysis or surgical removal of the mole.

  Prognosis

Moles are rarely cancerous and, once removed, unlikely to recur. A dermatologist should be consulted if a mole reappears after being removed.

  Prevention

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.

Anyone with a family history of melanoma should see a dermatologist for an annual skin examination. Everyone should know the ABCDs 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 the eraser on a pencil.

A mole exhibiting any of these characteristics should be evaluated by a dermatologist.

   Key Terms:

Malignant melanoma Most moles are benign, but atypical moles (called 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.

   Resources:

Books

• Harrison's Principles of Internal Medicine. Ed. Anthony S. Fauci, et al. New York: McGraw-Hill, 1997.

Organizations

• 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
• Nevus Outreach, Inc. 1601 Madison Blvd., Bartesville, OK 74006. (877) 426-3887. http://www.nevus.org

Other

• "Atypical Moles." The Skin Site. 8 Apr. 1998 http://www.skinsite.com/info_atypical moles.htm
• "Moles." American Academy of Dermatology. 7 Apr. 1998 http://www.aad.org
• "Moles." The Skin Site. 8 Apr. 1998 http://www.skinsite.com/info_moles.htm