Dysplastic Nevus (Atypical Moles)

What is dysplastic nevus (atypical mole)?

Dysplastic nevus is a mole that looks different from most moles. The mole may have irregular borders, be a mix of colors and appear larger than other moles.

Atypical moles are benign (not cancerous). However, having a lot of atypical moles increases your risk of melanoma, a life-threatening skin cancer. Atypical moles may also progress over time to become cancerous.

What are moles?

Specialized cells called melanocytes give your skin its color. When these skin cells clump together, they form moles (nevi).

Most people have harmless moles known as common moles. It’s normal for adults with light skin to have up to 40 common moles. Common and atypical moles tend to first appear during childhood and adolescence.

What does dysplastic nevus mean?

You may better understand this condition when you break down the meaning of each word:

• Dysplastic, or dysplasia, refers to the presence of unusual (abnormal) cells in tissue. Dysplastic tissue isn’t cancerous. But it has the potential to develop into cancer.
• “Nevus” is the medical term for a mole, a common type of skin growth. Nevi refers to multiple moles. Your provider may use the term dysplastic nevi if you have multiple atypical moles.

How common are dysplastic nevi (atypical moles)?

Atypical moles are common. Experts estimate that 1 in 10 Americans have at least one atypical mole.

Does dysplastic nevus cause skin cancer?

Having atypical moles increases your risk of melanoma. The more atypical moles you have, the greater the cancer risk. People who have 10 or more atypical moles are 12 times more likely to develop melanoma. Still, most people with atypical moles don’t develop melanoma.

Experts estimate that 1 in 4 cases of melanoma arises from a dysplastic nevus or atypical mole.

What are other words for dysplastic nevus?

Your healthcare provider may use these terms to refer to dysplastic nevus:

• Atypical mole.
• Clark’s nevi.
• Congenital nevus.
• Spitz nevus.

What causes dysplastic nevi (atypical moles)?

Experts aren’t sure why some people develop dysplastic nevi. A combination of genetics (family history) and environmental factors like ultraviolet (UV) light exposure may play a role.

What are sources of UV light?

The sun is a natural source of UV light. Artificial sources of UV light include:

• Certain halogen, incandescent and fluorescent lights, as well as some lasers.
• Mercury vapor lighting used in large venues like stadiums and gyms.
• Tanning beds and sunlamps.

Who is at risk for dysplastic nevi?

Atypical moles can affect people of all ages, sexes and skin colors. Having dark skin doesn’t protect you from atypical moles or skin cancer, but your risk is reduced.

People with these risk factors are more likely to develop atypical moles:

• Fair skin, freckles, light eyes and hair.
• Family history of atypical moles, skin cancer or melanoma.
• History of excessive sun exposure, sunburns or an inability to tan.
• Sensitivity to UV light (photosensitivity).

What do atypical moles look like?

An atypical mole (dysplastic nevus) may have some or all of these features:

• Flat with a pebbly or slightly raised surface.
• Irregular shape (not round) with blurry or ragged edges.
• Larger than a pencil eraser.
• Mix of colors, including pink, red, tan, brown and black.

Where do atypical moles appear?

Atypical moles can appear anywhere on your body. They most often appear on your trunk but can also show up on your:

• Extremities (arms and legs).
• Head.
• Neck.
• Scalp.

What are the complications of dysplastic nevi?

In addition to melanoma, having a lot of atypical moles may put you at risk for ocular melanoma. This type of cancer develops in your eyes. You may need more frequent eye exams.

How do healthcare providers diagnose dysplastic nevi (atypical moles)?

A dermatologist diagnoses and treats skin diseases like skin cancer. Seeing a skin cancer specialist is important when you have atypical moles. Your healthcare provider may perform:

• Skin examinations once or twice a year to check for changes to moles (or every three to six months if you have a family history of melanoma).
• Dermoscopy using a magnifying device called a dermatoscope to see abnormalities in moles that are invisible to the naked eye.
• Mole mapping using a special camera with a dermatoscopic lens to create a computerized map of your skin and moles.

How can you detect abnormal changes to moles?

You should perform skin self-exams regularly to look for changes to moles or skin. Healthcare providers recommend checking your skin at least once a month if you have atypical moles or other skin cancer risk factors. You can also take photographs to help detect changes from month to month.

You can use the ABCDE rule while checking moles for signs of skin cancer:

• Asymmetrical or irregular shape.
• Borders that are blurry, ragged or notched.
• Colors that include a mix of shades like browns, blacks, reds or blues.
• Diameter that’s larger than a pencil eraser (1/4 of an inch).
• Evolving changes over time, such as moles that grow in size, change shape or color, bleed or itch.

Contact a healthcare provider if you notice anything unusual, even if you think it’s nothing.

How are dysplastic nevi treated?

An atypical mole doesn’t need further treatment unless a skin biopsy indicates cancer or pre-cancerous changes. Your healthcare provider may use the terms atypical melanocytic hyperplasia or moderately to severely dysplastic to describe biopsy results. Such results indicate a higher risk of cancer. Your provider will then treat the mole with further surgery.

Treatments for atypical moles involve surgically removing the mole and a small border of surrounding skin. If the biopsy shows cancer (melanoma) associated with the atypical mole, your provider may perform a more extensive surgical removal or Mohs surgery, which helps preserve surrounding healthy tissue.

Can you prevent atypical moles?

While having atypical moles increases your risk of melanoma, removing benign normal moles doesn’t lower this risk.

There isn’t anything you can do to keep from having atypical moles. If you have them, you should take steps to protect your skin from sun damage and never use tanning beds.

What is the outlook for someone with dysplastic nevus?

Most people with atypical moles (as well as common moles) don’t develop skin cancer. Still, it’s important to examine your skin regularly for any unusual changes. Early detection and treatment of melanoma can be lifesaving.

What is atypical mole syndrome?

People who have atypical mole syndrome have large numbers of moles and an increased risk of melanoma. Most of the moles are common, but some are atypical moles. Some moles may be larger than a third of an inch in diameter.

A different condition called familial atypical multiple mole melanoma (FAMMM) syndrome affects members of the same family. An inherited gene mutation increases your risk of having atypical moles and melanoma. People with FAMMM syndrome are 25 times more likely to develop melanoma.

A note from Cleveland Clinic

Many people have atypical moles and never develop melanoma. But if you have atypical moles or dysplastic nevi, regular skin self-exams can help you quickly identify changes that may indicate a problem. Your healthcare provider can show you how to do these exams and tell you what changes to look for. Your provider may also recommend more frequent in-office skin exams, as well as eye exams. You should contact your provider any time you notice changes to your skin.