Dysplastic nevus (atypical mole)

Common moles tend to cover most adults with about 10 to 40 small, rounded, brown or black spots or growths in areas that get sun exposure. By age 40, people aren't likely to develop many new ones. Keeping an eye out for any changes to moles may be a critical way to prevent skin cancer. However, every mole is unique, and some look more abnormal than others.

What is a dysplastic nevus?

Dysplastic nevi are abnormal but noncancerous moles on the skin. They may be referred to as atypical moles or Clark’s nevus well. (If there’s only one mole, it’s called a dysplastic nevus.) Like other moles, they are surface growths that may change the skin’s color, typically to a darker one. About one in 10 people in the United States have at least one dysplastic nevus, according to the National Cancer Institute (NCI).

Dysplastic nevi are worth monitoring because they have some characteristics of a normal mole, but they also have some characteristics of melanoma skin cancer, including their size, shape and color. It’s rare for dysplastic nevi to turn into melanoma, though, and melanoma may develop without dysplastic nevi ever being present.

Dysplastic nevi and melanoma cancer

Although most dysplastic nevi don’t turn into melanoma, having one does increase the risk of developing melanoma cancer in a person's lifetime.

The more dysplastic nevi someone has, the higher the risk for melanoma. If someone has five or more dysplastic nevi, he or she has a 10 times greater risk of developing melanoma in his or her lifetime, as compared with someone with no dysplastic nevi, according to the NCI.

If melanoma does develop, it typically begins in a new spot on the skin and not from the dysplastic nevus itself. So even though there is a connection, having a dysplastic nevus doesn’t mean it’s likely to turn into melanoma. In fact, only about 25 percent of melanoma cases start from dysplastic nevi—most melanoma appear on their own, according to a 2022 review in StatPearls Publishing.

Melanoma cancer may develop in the eyes as well as on the skin. If a patient has dysplastic nevus syndrome, which involves having high numbers of dysplastic nevi, he or she is at higher risk of developing primary intraocular melanoma.

Dysplastic nevi symptoms

Dysplastic nevi stand out from normal moles in a few ways. They tend to appear on skin exposed to sun regularly, but they sometimes show up on the scalp, breasts or buttocks as well.

The symptoms of these atypical moles tend to be:

• Larger than common moles
• Flat with some parts that are raised
• Variable in terms of surface (they may be smooth, rough or scaly)
• Surrounded by an irregular border, have notched edges or fade into normal skin (they’re sometimes described as looking like a fried egg)
• Multicolored, including visibly distinct pink, red, tan, light brown or dark brown parts
• Relatively stable, changing a bit over time but not dramatically

Dysplastic nevi that are severe may look extremely similar to early melanoma.

Dysplastic nevi causes and risk factors

Dysplastic nevi are linked to a combination of environmental elements and genetics, but researchers are still studying exactly what causes them. Exposure to ultraviolet (UV) rays from the sun definitely plays a part.

The likelihood of developing dysplastic nevi is higher for people with:

• Light skin
• Skin that’s sensitive to the sun
• Light hair
• Light eye color
• Propensity to easily develop freckles

People with very high numbers of dysplastic nevi may have dysplastic nevus syndrome to blame. This inherited condition is also called atypical mole syndrome. Since dysplastic nevi often run in families, there is a genetic component to these moles.

If a close relative has had melanoma, this syndrome is referred to as familial atypical multiple mole melanoma syndrome (FAMMM), and it signals a significant lifetime risk of developing melanoma. Regular skin checks, both self-checks and those done by health care professionals, are key to preventing complications from melanoma.

Dysplastic nevi diagnosis

A doctor may be able to diagnose a dysplastic nevus with a physical exam alone. However, if the mole looks suspiciously like melanoma, as some dysplastic nevi do, the doctor may perform a biopsy to check a tissue sample for melanoma. If the initial biopsy doesn’t show melanoma, the care team likely won’t need to remove any more of the mole.

A diagnosis of dysplastic nevi is typically made if there are at least three of the following factors:

• Mole larger than 5 mm across
• Unclear or poorly defined borders
• Irregular margins between the mole and normal skin
• Color variation within the mole itself

Dysplastic nevi treatment

Treatment for dysplastic nevi that aren’t suspected melanoma is minimal, if any. If a dysplastic nevus is identified, the majority of work may fall to the patient to prevent any further skin conditions.

Dysplastic nevi patients should:

• Avoid suntans or sunburns by covering skin or using sunscreen when outside.
• Avoid tanning booths.
• Perform a skin check once a month.
• Schedule regular skin checks by a health care provider, varying in frequency based on the number of nevi and the degree of individual melanoma risk.

Most people don’t need dysplastic nevi removed because these aren’t cancerous. However, that doesn’t mean they should be ignored. Keep an eye out by doing regular skin checks.

Tell a doctor if the mole:

• Begins to bleed or ooze
• Changes in size or shape
• Becomes itchy
• Gets hard or feels lumpy
• Has any changes to the texture, especially if it becomes scaly or dry
• Begins to be more raised