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The information on this page was reviewed and approved by
Maurie Markman, MD, President, Medicine & Science at CTCA.

This page was updated on September 21, 2021.

Types of moles explained

Skin cancer, which forms on or within the skin, is the most common type of cancer in the United States. Basal cell carcinoma, squamous cell carcinoma and melanoma are the most common kinds of skin cancer.

Monthly skin self-exams may help you get to know your skin and its normal moles and markings. Check your skin, from head to toe, in front of a mirror in a well-lit room.

If you notice anything that looks out of the ordinary, such as a new mole or growth, you could potentially catch skin cancer early.

What should you look for?

When checking your skin, it’s important to know the difference between benign and cancerous moles. If you’re not sure, the ABCDE rule may help. ABCDE is an acronym for the signs and symptoms of skin cancer.

  • Asymmetry: A spot or mole on your skin with an unusual shape or two parts that don’t look the same
  • Border: A jagged or uneven border
  • Color: An uneven color
  • Diameter: A mole or spot that is larger than a pea
  • Evolving: A mole or spot that has changed within the past couple of weeks or months

Types of moles

Several kinds of moles, both benign and malignant, may form on the skin. These include common moles, dysplastic nevi and melanomas.

Common moles: When melanocytes, or skin pigment cells, grow in clusters, they form what’s called a common mole. They’re pink, tan or brown in appearance and look fairly even around the edges with a smooth surface. Common moles are typically benign, and adults often have 10 to 40 common moles on their skin. Babies sometimes are born with common moles, but most form with age (until about 40 years old) and in areas frequently exposed to the sun.

If you notice any changes in moles on your skin, such as those explained in the ABCDE rule, be sure to contact your doctor.

Dysplastic nevi: Also known as atypical moles, dysplastic nevi are often larger in size than a common mole. They’re typically flat and range in colors including pink and dark brown. They also:

  • Often measure more than 5 mm
  • Have a smooth, somewhat scaly or pebbly surface
  • Have an uneven edge, which fades into the skin around it

Most dysplastic nevi are found in sun-exposed areas of the body, but they may also occur in areas such as breasts, scalp and areas beneath the waist.

In most cases, dysplastic nevi don’t become melanoma skin cancer. However, the risk of skin cancer increases with greater numbers of dysplastic nevi.

If you have one or more dysplastic nevi, be sure to have your doctor take a look at them, especially if you have a family history of melanoma skin cancers. In addition, reach out to your doctor if you notice that your dysplastic nevus does the following:

  • Changes colors
  • Hardens or feels bumpy
  • Changes height, shape or texture
  • Itches
  • Oozes or bleeds
  • Increases or decreases in size
  • Feels scaly or dry around the surface skin

Melanoma: A type of skin cancer that starts in melanocytes, melanoma may stem from a common mole or dysplastic nevus, or it may develop in an area of the skin that appears normal. A melanoma may range in appearance, but one common sign is a change in the size of an existing or new mole that has a few or all of the ABCDE features, such as uneven borders and shades.

It occurs most often in people with fair skin. In people with darker skin, melanoma tends to form on the palms of the hand, under the fingernails, on the soles of the feet or under the toenails. In women, melanoma most often happens on the lower legs or back, whereas in men, melanoma is most commonly found on the back, neck or head.

The ABCDE rule may help you recognize signs and symptoms of early melanoma. However, in order to confirm whether a skin growth is cancerous, a doctor will need to remove tissue from the growth and have it sent to a lab for examination under a microscope.

What to do

If you’ve done a skin self-exam and you’re unsure whether a mole is benign or cancerous, you may:

  • Practice the ABCDE rule to see whether the mole’s characteristics match the signs and symptoms of melanoma.
  • Discuss any concerns about moles on your skin with your primary care doctor or dermatologist.
  • Ask your doctor about your risk factors, which may include:
    • Fair skin
    • High exposure to sunlight—a source of ultraviolet, or UV, rays that damage the skin—throughout your life
    • Dysplastic nevi on your skin
    • More than 50 common moles on your skin
    • Exposure to tanning beds
    • Certain medicines, such as particular antidepressants, antibiotics or hormones
    • Family history of skin cancer
    • Previous skin cancer diagnosis