What is a mole?

Moles (nevi is the medical term) are growths on the skin that range in color from the natural skin tone to brown or black. Moles can appear anywhere on the skin or mucous membranes, alone or in groups.

Most moles appear in early childhood and during the first 20 years of life. It is normal for a person to have between 10 to 40 moles by adulthood. Some moles may not appear until later in life.

The life cycle of an average mole is about 50 years. As the years pass, moles usually change slowly, becoming raised and lighter in color. Often, hairs develop on the mole. Some moles will not change at all and some will slowly disappear over time.

What causes a mole?

Moles occur when cells in the skin grow in a cluster instead of being spread throughout the skin. These cells are called melanocytes, and they make the pigment that gives skin its natural color. Moles may get darker after sun exposure, during pregnancy, and during puberty in the teen years.

What should I look for when examining my moles?

Most moles are benign (non-cancerous). The only moles that are of medical concern are those that look different than other existing moles (referred to as the ‘ugly duckling sign’) or those that appear after age 20. If you notice changes in a mole's color, thickness, size or shape, you should see a dermatologist. You also should have moles checked if they bleed, ooze, itch, or become tender or painful.

If your moles do not change over time, there is little reason for concern. However, if you notice changes in a mole's color, thickness, size, or shape, you should see a dermatologist. You also should have moles checked if they bleed, ooze, itch, or become tender or painful.

Examine your skin with a mirror or ask someone to help you. Pay special attention to areas of your skin that are often exposed to the sun, such as the face, hands, legs (especially in females), arms, chest, and back (men).

The ABCDE's are important signs of moles that could be cancerous. If a mole displays any of the signs listed below, have it checked immediately by a dermatologist:

  • Asymmetry: If one half of the mole does not match the other half
  • Border: If the border or edges of the mole are ragged, blurred or irregular
  • Color: If the color of the mole is not the same throughout, or it has shades of multiple colors such as tan, brown, black, blue, white, or red
  • Diameter: If the diameter of a mole is larger than the eraser of a pencil
  • Elevation/Evolution: If the mole becomes raised after being flat, or it changes over time

The most common location for melanoma (form of skin cancer) in men is the back; in women, it is the lower leg. Melanoma is the most common cancer in women ages 25 to 29.

What are the different types of moles?

Congenital Nevi: These are moles that appear at birth. Congenital nevi occur in about 1 in 100 people. These moles may be more likely to develop into melanoma than moles that appear after birth. If the mole is more than eight inches in diameter, it has a greater risk of becoming cancerous.

Dysplastic Nevi: These moles are larger than a pencil eraser and irregularly shaped. Dysplastic nevi tend to have uneven color with dark brown centers and lighter, uneven edges. These moles tend to be hereditary (inherited), and people who have them may have more than 100 moles. People with dysplastic nevi have a greater chance of developing malignant (cancerous) melanoma. Any changes in the mole should be checked by a dermatologist to detect skin cancer.

How does your dermatologist determine if moles are a concern?

Normal (benign) moles do not need to be removed. (Doing so will leave a scar.)

If your dermatologist determines that the mole is a concern, he or she will perform a skin biopsy, in which a small sample of the mole is taken to examine under a microscope. A diagnosis can usually be made in less than a week. If the mole is found to be cancerous, it needs to be completely removed.

If you are concerned that a mole is changing or if you see worrisome signs, please call your dermatologist to have the mole examined.


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This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition. This document was last reviewed on: 3/22/2017...#4410