A mole is a growth on the skin that can be flesh-colored, brown, or black. Moles can appear anywhere on the skin, alone or in groups.

Most moles appear during the first two decades of a person’s life, though some may not appear until later in life. It is normal to have between 10 and 40 moles by adulthood. As a person ages, moles usually change slowly – becoming raised, changing color, or slowly disappearing. Oftentimes hairs grow out of the mole.

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. They make the pigment, called melanin, which gives skin its natural color. Moles may darken after exposure to the sun, during the teen years and during pregnancy. The most common cause of moles is heredity. Many doctors also believe that overexposure to ultraviolet rays (sunlight) causes moles to form.


What are congenital nevi?

Congenital Nevi are moles that appear at birth. Occurring in about one in 100 people, these moles may be more likely to develop into melanoma (cancer) than moles that appear after birth. If the mole is more than eight inches in diameter it poses a significant risk of becoming cancerous.

What are dysplastic or atypical nevi?

Dysplastic or Atypical Nevi are benign (non-cancerous) moles that may share some of the characteristics of a melanoma (cancer), but are not a melanoma or any other form of cancer. The presence of an atypical or dysplastic nevus, however, may increase the risk of developing melanoma. The risk increases with the number of atypical or dysplastic nevi present. These moles tend to be hereditary.

How do I know if a mole is cancerous?

Most moles are not dangerous. 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.

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, talk to your dermatologist. 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.

The following ABCDEs are important characteristics to consider when examining your moles. If a mole displays any of the signs listed below, have it checked immediately by a dermatologist. It could be cancerous.

  • A – Asymmetry – One half does not match the other half in size, shape, color or thickness.
  • B – Border Irregularity – The border or edges are ragged, blurred, or irregular.
  • C – Color – The pigmentation of the mole is not uniform or has shades of tan, brown, black, blue, white, or red.
  • D – Diameter – The diameter of a mole is larger than the eraser of a pencil.
  • E – Elevation – A portion of the mole appears elevated, or raised, from the skin; or Evolution – Change occurring in a mole.

See our Skin Cancer page for more information.

How are moles treated?

If your dermatologist believes a mole needs to be evaluated further or removed entirely, he or she will either remove the entire mole, or first take just a small tissue sample of the mole to examine thin sections of the tissue under a microscope (a biopsy). This is a simple procedure. If the mole is found to be cancerous and only a small section of tissue was taken, the dermatologist will remove the entire mole by cutting out the entire mole and a rim of normal skin around it.

Your risks of skin cancer can be reduced when you protect yourself from the sun, are aware of suspicious growths, and visit a dermatologist for regular skin checks.

Additional Resources About Moles