What is an atypical mole

Atypical mole also called atypical nevus or dysplastic mole (dysplastic nevus), is benign melanocytic nevus with irregular and ill-defined borders, variegated colors usually of brown and tan tones, and macular or papular components. Patients with atypical moles have an increased risk of melanoma. Management is by close clinical monitoring and biopsy of highly atypical or changed lesions. Patients should reduce sun exposure and conduct regular self-examinations for new moles or changes in existing ones.

Atypical moles are very common. An estimated one out of every 10 Americans (about 33 million people) have at least one atypical mole ¹. Atypical moles are larger than common moles, with borders that are irregular and poorly defined. Atypical moles also vary in color, ranging from tan to dark brown shades on a pink background. They have irregular borders that may include notches. They may fade into surrounding skin and include a flat portion level with the skin. These are some of the features that one sees when looking at a melanoma. When a pathologist looks at an atypical mole under the microscope, it has features that are in-between a normal mole and a melanoma.

Atypical mole is caused by collections of the color-producing (pigment-producing) cells of the skin (melanocytes) in which the cells grow in an abnormal way. Atypical moles may occur as new lesions or as a change in an existing mole. Atypical mole may be single or multiple. In atypical-nevus syndrome, hundreds of atypical moles may be seen. People with atypical moles may be at increased risk for developing skin cancer (melanoma), with the risk increasing with the number of atypical moles present.

For years, doctors have debated the risk of developing melanoma in people with atypical moles. Melanoma is a potentially deadly form of skin cancer that is diagnosed in about 40,000 Americans each year. It is now known that about half of the people with melanoma have numerous atypical moles on their bodies. The risk is greatest in people who also have extremely fair skin and heavy freckling, a sign of excessive sun exposure.

While atypical moles are considered to be pre-cancerous (more likely to turn into melanoma than regular moles), not everyone who has atypical moles gets melanoma. In fact, most moles — both ordinary and atypical ones — never become cancerous. Thus the removal of all atypical nevi is unnecessary. In fact, most of the melanomas found on people with atypical moles arise from normal skin and not an atypical mole.

Still, there is potentially great benefit in identifying persons at increased risk of melanoma. Individuals and family members with atypical moles from melanoma-prone families should be closely checked for melanomas. This has resulted in the diagnosis of a substantial number of curable melanomas.

People without a family history of atypical moles or melanoma have an increased risk of melanoma, but it is not as high as the risk observed in members of melanoma-prone families. Individuals with a single atypical mole on their bodies have a twofold risk of developing melanoma. The risk rises to 14-fold in those with 10 or more abnormal moles.

If there are a great many atypical moles and several family members have had melanoma, you need to be very careful. Still, it has not been shown that removing all the moles (sometimes in the hundreds) decreases the lifetime risk for melanoma. Melanoma usually arises de novo, i.e. not in a pre-existing benign mole. Also people with atypical moles should have annual eye exams, as ocular melanoma is also a big risk in these cases. One should be followed closely with a very low threshold to biopsy any lesion remotely suspicious. Getting detailed body photographs are an excellent way to follow moles to see if any are changing.

Although a physician bases the initial diagnosis of atypical moles on a physical examination, removing several moles and examining them under a microscope must confirm the diagnosis. This procedure, called a biopsy, is usually performed in your doctor’s office using local anesthesia.

A pathologist will examine the tissue under a microscope and make the precise diagnosis. Diagnosis by biopsy is not exact, and in difficult cases doctors may split 50/50 down the middle as to whether a mole is melanoma or benign. If the pathologist uses the term “severely dysplastic” or “atypical melanocytic hyperplasia” or offers a long descriptive narrative it means he really is concerned about melanoma, but does not want to call it that.

Most dermatologists usually recommend that all patients with these severely dysplastic moles have them removed with a margin (0.5 cm-about a quarter inch) of clinically normal skin. Also many dermatologists recommend removing “moderate dysplasia” moles, if the biopsy didn’t get all of it. Those with “mild dysplasia” can usually be left alone or watched.

Once the diagnosis of atypical moles is established, additional biopsies are performed only if melanoma is suspected, or if a new mole appears. Just as women who regularly examine their own breast are much more likely to be cured of breast cancer if it appears, self-exam of your skin once a month is the best defense against melanoma. Be sure to insist on a biopsy of any mole that is changing or growing.

Atypical mole key points

• Risk of melanoma is higher if patients have increased numbers of atypical moles, increased sun exposure, or familial atypical mole–melanoma syndrome.
• Because clinical differentiation from melanoma can be difficult, biopsy the worst-appearing atypical moles.
• Closely follow patients with atypical moles, particularly those at higher risk of melanoma, and do full-body photography.
• Recommend sun protection (with supplemental vitamin D) and self-examination for high-risk changes.
• Do full-body examinations of all 1st-degree relatives of patients who have melanoma.

Can a atypical mole turn into melanoma?

Yes, but most atypical moles do not turn into melanoma ². Most remain stable over time. Researchers estimate that the chance of melanoma is about ten times greater for someone with more than five atypical moles than for someone who has none, and the more atypical moles a person has, the greater the chance of developing melanoma ³.

What should people do if they have a atypical mole?

Everyone should protect their skin from the sun and stay away from sunlamps and tanning booths, but for people who have atypical moles (dysplastic nevi), it is even more important to protect the skin and avoid getting a suntan or sunburn.

In addition, many doctors recommend that people with atypical moles check their skin once a month ⁴. People should tell their doctor if they see any of the following changes in a atypical mole ⁴:

• The color changes
• It gets smaller or bigger
• It changes in shape, texture, or height
• The skin on the surface becomes dry or scaly
• It becomes hard or feels lumpy
• It starts to itch
• It bleeds or oozes

Another thing that people with atypical moles (dysplastic nevi) should do is get their skin examined by a doctor ⁵. Sometimes people or their doctors take photographs of atypical moles (dysplastic nevi) so changes over time are easier to see ⁴. For people with many (more than five) atypical moles, doctors may conduct a skin exam once or twice a year because of the moderately increased chance of melanoma. For people who also have a family history of melanoma, doctors may suggest a more frequent skin exam, such as every 3 to 6 months ³.

Should people have a doctor remove a atypical mole or a common mole to prevent it from changing into melanoma?

No. Normally, people do not need to have a atypical mole or common mole removed. One reason is that very few atypical moles (dysplastic nevi) or common moles turn into melanoma ². Another reason is that even removing all of the moles on the skin would not prevent the development of melanoma because melanoma can develop as a new colored area on the skin ⁴. That is why doctors usually remove only a mole that changes or a new colored area on the skin.

Who’s at risk of developing atypical mole?

• Atypical moles may occur at any age and in all ethnic groups.
• Atypical moles frequently run in families.
• People with atypical moles may have a family history of melanoma.

Atypical mole signs and symptoms

• Atypical moles may appear anywhere on the skin. The lesions can vary in size and/or color. A atypical mole may occur anywhere on the body, but it is usually seen in areas exposed to the sun, such as on the back. A atypical mole may also appear in areas not exposed to the sun, such as the scalp, breasts, and areas below the waist ². Some people have only a couple of atypical moles, but other people have more than 10. People who have atypical moles usually also have an increased number of common moles.
• Atypical moles can be larger than a pencil eraser (6 mm) and may have variations in color within the lesion ranging from pink to reddish-brown to dark brown.
• Atypical moles may be darker brown in the center or in the edges (periphery).
• People with atypical-nevus syndrome may have hundreds of moles of varying sizes and colors.

Atypical mole prevention and self-care

Sun protection such as avoiding skin exposure to sunlight during peak sun hours (10 AM to 3 PM), wearing sun-protective clothing, seeking shade and applying high-SPF sunscreen, are essential for reducing exposure to harmful ultraviolet (UV) light.

Monthly self-examination of the skin is helpful to detect new lesions or changes in existing lesions.

Full-body photography

Sometimes surveillance of family members

Be sure your atypical moles are not signs of skin cancer (melanoma). Remember the ABCDEs of melanoma lesions:

• A – Asymmetry: One half of the lesion does not mirror the other half.
• B – Border: The borders are irregular or vague (indistinct).
• C – Color: More than one color may be noted within the mole.
• D – Diameter: Size greater than 6 mm (roughly the size of a pencil eraser) may be concerning.
• E – Evolving: Notable changes in the lesion over time are suspicious signs for skin cancer.

Atypical mole diagnosis

Although clinical findings can sometimes establish a diagnosis of atypical moles, visual differentiation between atypical nevi and melanoma can be difficult; biopsy of the worst-appearing lesions should be done to establish the diagnosis and to determine the degree of atypia. Biopsy should aim to include the complete depth and breadth of the lesion; excisional biopsy is often ideal.

Patients with multiple atypical moles and a personal or family history of melanoma should be examined regularly (eg, yearly for family history of melanoma, more often for personal history of melanoma). Some dermatologists do imaging of the skin using a hand-held instrument (dermoscopy) to see structures not visible to the naked eye. Dermoscopy can reveal certain high-risk characteristics (eg, blue-white veil, irregular dots and globules, atypical pigment network, reverse network).

Atypical mole treatment

• Biopsy or surgical removal (excision) may be done so the mole may be examined by a specialist (pathologist) to determine the actual diagnosis.
• As noted previously, people with multiple moles and atypical moles should be followed regularly by a dermatologist. Whole-body photography or photographs of individual moles may be helpful in following these people.

Atypical moles may warrant removal for any of the following conditions:

• A patient has a high-risk history (eg, personal or family history of melanoma).
• A patient cannot guarantee close follow-up.
• The mole has high-risk dermatoscopic findings.
• The mole is in a location that makes monitoring the lesion for changes difficult or impossible for the patient.

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