Moles (pigmented nevi is the medical term) are growths on the skin that usually are flesh-colored, brown or black. Moles can appear anywhere on the skin, alone or in groups.

Most moles appear in early childhood and during the first 20 years of a person's 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. Some moles 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 darken after exposure to the sun, during the teen years and during pregnancy.

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 or those that first appear after age 20. If you notice changes in a mole's color, height, size or shape, you should have a dermatologist evaluate it. You also should have moles checked if they bleed, ooze, itch, appear scaly 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 hands, arms, chest, neck, face and ears.

If your moles do not change over time, there is little reason for concern.

The following ABCD'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: When one half of the mole does not match the other half
  • Border: When the border or edges of the mole are ragged, blurred or irregular
  • Color: When the color of the mole is not the same throughout or if it has shades of tan, brown, black, blue, white or red
  • Diameter: If the diameter of a mole is larger than the eraser of a pencil

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:

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 are moles that appear after birth. If the mole is more than 8 inches in diameter, it poses a significant risk of becoming cancerous.

Dysplastic Nevi:

Moles that are larger than average (larger than a pencil eraser) and irregular in shape. They tend to have uneven color with dark brown centers and lighter, uneven edges. These moles tend to be hereditary, and people with dysplastic nevi 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 are moles treated?

To treat a mole, first a biopsy (small tissue sample of the mole) is taken by a dermatologist so that thin sections of the tissue can be examined under a microscope. This is a simple procedure. If the dermatologist thinks the mole might be cancerous, cutting through the mole will not cause the cancer to spread. If the mole is found to be cancerous, the dermatologist will remove the entire mole.

There are two methods of removal:
  • Removing the mole by shave excision (shaving it off)
  • Cutting out the entire mole and stitching the area closed
  • If you see any signs of change in an existing mole, if you have a new mole or if you want a mole to be removed for cosmetic reasons, consult your dermatologist.

Where can I get more information?

Reviewed by a Cleveland Clinic medical professional.

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