What’s the Difference Between Dysplastic Nevus and Melanoma?

Moles can be distinctive (think: Cindy Crawford and Marilyn Monroe) but they can also be deadly. Having numerous moles that are considered to be atypical (also called dysplastic) can substantially increase your risk of melanoma, according to the American Osteopathic College of Dermatology (AOCD). And about 10% of Americans have at least one atypical mole, per the AOCD.

When it comes to distinguishing common moles from abnormal moles that may signify melanoma, simply eyeballing one won’t tell you much, especially if you’re not a dermatologist. Taking a closer look at the mole pattern across your entire body, as well as a magnified analysis and possibly tissue testing, can help your doctor figure out if that brownish bump is cause for concern or just another beauty mark.

Moles can come in different sizes, shapes, and colors, and there are some clear distinctions between what is considered normal and what may be potentially dangerous.

Moles

The medical term for a mole is nevus (or nevi, if plural). A mole is a benign cluster or collection of melanocytes, pigmented skin cells that are interspersed throughout the epidermal layer of skin, explains Pedram Gerami, M.D., a professor of dermatology at Northwestern Medicine Feinberg School of Medicine in Chicago. “In normal skin there’s one melanocyte for every 40 epidermal cells,” he says. “A mole is like a colony of melanocytes.”

A typical mole is a small brown spot (usually less than ¼ inch in diameter) that is oval or round, per the Mayo Clinic. It may also be tan, black, blue, red, or pink and can be raised, flat, smooth or wrinkled. If you were born with the mole, it’s called a congenital nevus, but most can be acquired as you grow and age.

Dysplastic Nevus

A dysplastic nevus is “a benign collection of melanocytes [i.e., a mole] that’s growing in a pattern that somewhat mimics the superficial spreading type of melanoma,” explains Dr. Gerami. A dysplastic nevus, sometimes called a Clark’s nevus, is a type of atypical (not normal) nevus—but not all atypical nevi are dysplastic, he cautions.

“These moles have clinical features that are atypical, such as being a little large, varying in color, or having irregular borders, so they’re concerning, but they’re benign,” says Emily Smith, M.D., an associate professor of dermatology at Saint Louis University School of Medicine in Missouri. “They are not pre-melanomas.” Still, people who have more than 10 atypical moles have 12 times the risk of developing melanoma, according to the Skin Cancer Foundation.

“People can form moles that don’t look typical, called signature nevi,” adds Anuj Kunadia, M.D., a senior dermatology resident at the University of Oklahoma College of Medicine in Oklahoma City. “If you have one in isolation, it’s concerning, but if you have 30 other similar-looking moles around your body, then we’re not as worried.” But if one of those unusual moles looks significantly different than the rest—called the ugly duckling sign—your dermatologist may think about taking a biopsy, he explains. “We’re looking for patterns and outliers,” says Dr. Kunadia.

Melanoma

A melanoma is a malignant collection of melanocytes, says Dr. Gerami. The most common type of melanoma—accounting for about 70% of cases, according to Memorial Sloan Kettering Cancer Center—grows flat on the surface of the skin and has irregular color or borders. It’s called the superficial spreading type. “If you look at superficial melanoma, two-thirds of those form in an area where there’s normal skin, where there was no mole to start with,” says Dr. Gerami. Still, wherever you have a mole of any type, there’s a higher, albeit small, chance of getting a melanoma, he says.

Moles that look different than other existing moles on your body, or those that appear on your skin after age 30, are also at a higher risk of being classified as melanoma, per the Cleveland Clinic. Changes in mole color, thickness, size, or shape should also be examined by a dermatologist.

The first step in diagnosing dysplastic nevi is to do a full skin exam with your dermatologist, who will look over your entire body to see what your mole pattern is, if you have one, and then zeroing in on any lesions (abnormal spots) in question. As they do for all moles, your dermatologist will check for the ABCDEFs that can potentially signal skin cancer. These include:

• Asymmetry (one half doesn’t match the other)

• Borders that are irregular

• Color (varying shades that may include brown, black, red, pink, or even blue)

• Diameter (anything beyond 6mm or ¼-inch wide is suspicious)

• A lesion that is evolving over time.

• A “funny looking” mole that’s out of the norm for your particular mole pattern

Since both dysplastic nevi and melanoma can have these features, your doctor will likely use a dermatoscope, a handheld device that magnifies the skin, to get a closer look and check for atypical vascular patterns. This helps differentiate dysplastic nevi from melanoma, says Dr. Smith. If your doctor is confident a mole is a dysplastic nevus, there may be no need for any testing, since they’re benign, but they’ll monitor it over time.

However, the only way to know for sure if a nevus is dysplastic or melanoma is by taking a biopsy and looking at it under a microscope. “Using histologic criteria, we can be certain of whether a nevus is dysplastic or melanoma in 95% to 98% of cases,” says Dr. Gerami. “But we only biopsy the ones that we think could be melanoma.”

Once a lesion has been biopsied, a pathologist will type and grade it. There are a few different types of dysplastic nevi that are characterized by the number and type of cell changes. The word atypia is used to describe an abnormality in cells in tissue.

Dysplastic Nevus With Mild Atypia

In most cases, these won’t even be biopsied because your doctor likely won’t be suspicious of them being a melanoma. But if it is biopsied and graded as “mild,” it just means the nevus is growing in a way that’s atypical compared to a common acquired nevus, says Dr. Smith. “This is normal for a dysplastic nevus.”

Dysplastic Nevus With Moderate Atypia

This means the nevus has more atypical features, “maybe an extra degree outside the ‘norm’ for a dysplastic nevus,” says Dr. Smith. “This is the most difficult one to classify, but it’s still benign.” The American College of Dermatology has determined there is no need for further excision (removal) of a nevus if it’s mild or moderate atypia, says Dr. Smith. However, your doctor will still likely want to monitor it to make sure it doesn’t change or show any signs that it is in fact a melanoma. Some people may decide they want the nevus removed entirely regardless of the diagnosis, she adds, but these moles are much less frequently excised today than they were a couple of decades ago.

Dysplastic Nevus With Severe Atypia

These nevi have features that are suggestive of what is seen in a melanoma, but they’re still benign, says Dr. Smith. If a nevus is graded severe, your doctor will likely want to go back and remove the full lesion (if they didn’t do that to begin with), although ultimately it’s up to you. “We tend to lean toward over-excising out of precaution,” she says. Research has shown that moderately to severe dysplastic nevi are more often associated with melanomas.

Per the Cleveland Clinic, dysplastic nevi may include a mole with some or all of the following:

• Flat with a pebbly or slightly raised surface

• Irregular shape with blurry or ragged edges

• Larger than a pencil eraser

• Mix of colors (including pink, red, tan, brown, and black)

Per the American Cancer Society, melanoma can include some of the following symptoms:

• A new spot on the skin or a spot that is changing in size, shape, or color or is scaling, flaking, bleeding, or painful

• A spot that looks different from all of the other spots (the “ugly duckling” sign)

• Moles that include some of the ABCDEF criteria

As you can see, these descriptions overlap and can be hard to parse apart, which is why you should see your dermatologist if you develop any of the above symptoms. If a melanoma has metastasized (spread) to other parts of the body—such as the pancreas, brain, liver, or lungs—there may be signs and symptoms associated with that spread, such as weight loss, fatigue, unexplained lumps under the skin, or jaundice.

The risk factors for both dysplastic nevi and melanoma are similar, says Dr. Gerami. These can include the following:

• Family history: Your risk of melanoma is higher if one or more of your first-degree relatives (parents, brothers, sisters, or children) has had this cancer, per the American Cancer Society. Genetics also factors in the development of dysplastic nevus, according to the Cleveland Clinic.

• Exposure to ultraviolet rays, via the sun or using a tanning bed, can also cause moles to form, in addition to causing melanoma itself.

• Your immune system may also play a role as well, as it can contribute to more growths forming, says Dr. Gerami.

• People with fair skin, light-colored eyes, and light hair have a higher risk of developing melanoma, according to UPMC Hillman Cancer Center.

• Age and sex can affect the risk of developing melanoma. The risk of melanoma increases as you age, although it can develop in younger people. Before age 50, women are more likely than men to get melanoma, per the American Cancer Society; after age 50 the risk is higher in men.

While very few dysplastic nevi turn into melanoma, having many of them is a risk factor for developing melanoma. In a study published in JAMA Dermatology, researchers concluded that having two or more biopsied dysplastic nevi, with one being moderate atypia, is associated with an increased risk of developing melanoma elsewhere on the body.

Having more than 50 moles or dysplastic nevi—sometimes called atypical mole or dysplastic nevus syndrome—can also put you at risk for melanoma, says Dr. Smith. If you have a bunch of these moles and a family member with melanoma, you may have an inherited condition called familial atypical multiple mole melanoma syndrome, which can increase your risk for melanoma as well as pancreatic and other cancers, says Dr. Kunadia.

Mild and moderate atypia nevi don’t need further treatment, says Dr. Smith. If your doctor didn’t do a complete excision for the biopsy of a suspected severe atypia nevus, they may go back and ensure all the borders have been removed. If pathology determines a lesion is melanoma, full removal, including borders around it, is the only treatment. “Where it is on your body and the type of melanoma will determine the type of surgical treatment you need,” says Dr. Smith.

Depending on the staging of the melanoma, your doctor may biopsy lymph nodes closest to the lesion to check for spreading. “Most of the time, if a melanoma does metastasize, it will go to the lymphatic system first,” says Dr. Kunadia. “If positive, then you have more aggressive options available. People with metastatic melanoma may benefit from immunomodulators that help the immune system attack areas of the body that are affected. It depends on the staging and the type of melanoma.”

Although you can’t control your genetics or the growth of moles, there are some things you can do to reduce your risk of developing dysplastic nevi and melanoma, according to the American Cancer Society:

• Avoid UV exposure, including tanning beds, especially during peak sun hours of the day (10 a.m. to 4 p.m.).

• Wear sunscreen, at least SPF 30, and use a hat, clothing, and sunglasses to protect you from prolonged sun exposure.

• Get regular skin checks—including doing self-inspection—especially if you have many moles or a family history of melanoma.

• Keep your kids from getting sunburns by making sure they wear sunscreen and stay out of the sun when possible, especially during peak hours.

Having a lot of moles or dysplastic nevi can increase the likelihood of getting melanoma at some point in your life, says Dr. Gerami, but the most common type of melanoma usually develops on normal skin. Dysplastic nevi don’t need to be removed, although your doctor, with your input, may decide it’s easier to take it out completely for peace of mind and to minimize any risk that it could become melanoma.

Early detection is key for optimizing outcomes and survival for melanoma, says Dr. Smith. Talk to your doctor about any suspicious or changing moles and tell them if you have a family history of melanoma. They may want to track your nevi with total-body photography to compare your skin from appointment to appointment.