Overview

Moles are a common type of growth on the skin. They often appear as small, dark brown spots and are caused by clusters of pigmented cells. Moles generally appear during childhood and adolescence. Most people have 10 to 45 moles, almost all of which appear before age 40. Some moles may fade or disappear as you age.

Most moles are harmless. Rarely, they become cancerous. Monitoring moles and other pigmented patches is an important step in detecting skin cancer, especially malignant melanoma.

The medical term for moles is nevi.

Symptoms

The typical mole is a brown spot. But moles come in a wide variety of colors, shapes and sizes:

  • Color and texture. Moles can be brown, tan, black, red, blue or pink. They can be smooth, wrinkled, flat or raised. They may have hair growing from them.
  • Shape. They can vary in shape from oval to round.
  • Size. Moles are usually less than 1/4 inch (about 6 millimeters) in diameter — the size of a pencil eraser. Rarely, moles present at birth can be much bigger, covering wide areas of the face, torso or a limb.

Moles can develop anywhere on your body, including your scalp, armpits, under your nails, and between your fingers and toes. Most people have 10 to 45 moles. Most of these develop by age 40. Moles may change in appearance over time — some may even disappear with age. Hormonal changes of adolescence and pregnancy may cause moles to become darker, larger and more numerous.

Unusual moles that may indicate melanoma

This ABCDE guide can help you determine if a mole or a spot may be melanoma:

  • A is for asymmetrical shape. One half is unlike the other half.
  • B is for border. Look for moles with irregular, notched or scalloped borders.
  • C is for color. Look for growths that have changed color, have many colors or have uneven color.
  • D is for diameter. Look for new growth in amole larger than 1/4 inch (about 6 millimeters).
  • E is for evolving. Watch for moles that change in size, shape, color or height, especially if part or all of a mole turns black.

Cancerous (malignant) moles vary greatly in appearance. Some may show all of the features listed above. Others may have only one or two.

When to see a doctor

See your doctor if you have a mole that:

  • Is painful
  • Itches or burns
  • Oozes or bleeds
  • Shows any of the ABCDE characteristics listed above
  • Grows back after having been removed before
  • Is new and you're over 30 years old

If you're concerned about any mole, see your doctor or ask for a referral to a doctor who specializes in skin conditions (dermatologist).

Causes

Moles are caused when cells in the skin, called melanocytes, grow in clusters or clumps. Melanocytes are distributed throughout your skin and produce melanin, the natural pigment that gives your skin its color.

Complications

Melanoma is the main complication of moles. Some people have a higher than average risk of their moles becoming cancerous and developing into melanoma. Factors that increase your risk of melanoma include:

  • Being born with large moles. These types of moles are called congenital nevi. On an infant, such moles are classified as large if they're more than 2 inches (5 centimeters) in diameter. Even a large mole seldom becomes cancerous and almost never before the child reaches puberty.
  • Having unusual moles. Moles that are bigger than a common mole and irregular in shape are known as atypical (dysplastic) nevi. They tend to be hereditary. And they often have dark brown centers and lighter, uneven borders.
  • Having many moles. Having more than 50 ordinary moles on your body indicates an increased risk of melanoma. Two recent studies add to the evidence that the number of your moles predict cancer risk. One showed that people with 20 or more moles on their arms are at increased risk of melanoma. Another showed a relationship between the number of women's moles and breast cancer risk.
  • Having a family history of melanoma. Some types of atypical moles lead to a genetic form of melanoma.

Prevention

The following measures can help limit the development of moles and the main complication of moles — melanoma.

Watch for changes

Become familiar with the location and pattern of your moles. Regularly examine your skin carefully to look for skin changes that may signal melanoma. Ideally, do self-exams once a month, especially if you have a family history of melanoma.

Do a head-to-toe check, including your scalp, palms and fingernails, armpits, chest, genital area, feet (the soles, toenails and between the toes), and between the buttocks. If necessary, use a hand-held mirror along with a wall mirror to scan hard-to-see places, such as your back.

If you have many moles or unusual-looking moles, you may want to have a full-body mole check by a dermatologist.

To detect melanomas or other skin cancers, use this ABCDE skin self-examination guide:

  • A is for asymmetrical shape. Look for moles with irregular shapes, such as two very different-looking halves.
  • B is for border. Look for moles with irregular, notched or scalloped borders.
  • C is for color. Look for growths that have changed color, have many colors or have uneven color.
  • D is for diameter. Look for new growth in amole larger than 1/4 inch (about 6 millimeters).
  • E is for evolving. Watch for moles that change over weeks or months.

Protect your skin

Take measures to protect your skin from ultraviolet (UV) radiation, such as from the sun or tanning beds. UV radiation has been linked to increased melanoma risk. And children who haven't been protected from sun exposure tend to develop more moles.

  • Avoid peak sun times. It's best to avoid overexposure to the sun. If you must be outdoors, try to stay out of the sun from 10 a.m. to 4 p.m., when UV rays are strongest.
  • Use sunscreen year-round. Apply sunscreen about 30 minutes before going outdoors, even on cloudy days. Use a broad-spectrum sunscreen with an SPF of at least 15. Apply it generously and reapply every two hours — or more often if you're swimming or sweating. The American Academy of Dermatology recommends using a broad-spectrum, water-resistant sunscreen with an SPF of at least 30.
  • Cover up. Sunglasses, broad-brimmed hats, long sleeves and other protective clothing can help you avoid damaging UV rays. You might also want to consider clothing that's made with fabric specially treated to block UV radiation.
  • Avoid tanning beds. Tanning beds emit UV rays and can increase your risk of skin cancer.
Dec. 06, 2014
References
  1. Moles. MedlinePlus. http://www.nlm.nih.gov/medlineplus/moles.html. Accessed Sept. 10, 2014.
  2. Argenziano G, et al. Twenty nevi on the arms: A simple rule to identify patients younger than 50 years of age at higher risk for melanoma. European Journal of Cancer Prevention. 2014;23:458.
  3. Wise J. Number of moles could predict breast cancer risk. BMJ. 2014;348:g3739. http://www.bmj.com/content/348/bmj.g3739.full.print? Accessed Sept. 10, 2014.
  4. Goldsmith LA, et al., eds. Fitzpatrick's Dermatology in General Medicine. 8th ed. New York, N.Y.: The McGraw-Hill Companies; 2012. http://accessmedicine.mhmedical.com/book.aspx?bookid=392. Accessed Sept. 10, 2014.
  5. Prevention guidelines. Skin Cancer Foundation. http://www.skincancer.org/prevention/sun-protection/prevention-guidelines. Accessed Sept. 10, 2014.
  6. Gibson LE (expert opinion). Mayo Clinic, Rochester, Minn. Sept. 19, 2014.
  7. What does a mole look like? National Cancer Institute. http://www.cancer.gov/cancertopics/prevention/skin/molephotos. Accessed Sept. 10, 2014.
  8. Common moles, dysplastic nevi, and risk of melanoma. http://www.cancer.gov/cancertopics/factsheet/Risk/moles. Accessed Sept. 10, 2014.
  9. Hawryluk EB, et al. Pediatric melanoma, moles, and sun safety. Pediatric Clinics of North America. 2014;61:279.
  10. Sunscreens. American Academy of Dermatology. http://www.aad.org/media-resources/stats-and-facts/prevention-and-care/sunscreens#.UbdQaJzm9lP. Accessed Nov. 20, 2014.
  11. FDA sheds light on sunscreens. U.S. Food and Drug Administration. http://www.fda.gov/ForConsumers/ConsumerUpdates/ucm258416.htm. Accessed Nov. 20, 2014.
  12. Moles in children: What parents should know. American Academy of Dermatology. http://www.skincarephysicians.com/skincancernet/moles_children.html. Accessed Sept. 10, 2014.
  13. What you need to know about melanoma and other skin cancers. National Cancer Institute. http://www.cancer.gov/cancertopics/wyntk/skin. Accessed Sept. 12, 2014.
  14. Niederhuber JE, et al., eds. Abeloff's Clinical Oncology. 5th ed. Philadelphia, Pa.: Churchill Livingstone Elsevier; 2014. http://www.clinicalkey.com. Accessed Sept. 12, 2014.
  15. Habif TP. Clinical Dermatology: A Color Guide to Diagnosis and Therapy. 5th ed. Edinburgh, U.K.; New York, N.Y.: Mosby Elsevier; 2010. http://www.clinicalkey.com. Accessed Sept. 12, 2014.
  16. Skin examinations. SkinCancerNet. http://www.skincarephysicians.com/skincancernet/skin_examinations.html. Accessed Sept. 12, 2014.