Unusual Nevi—Insignificant Ugly Ducklings

Selected by Pietro Cazzola


In this interview, PracticeUpdate talks with Jennifer A. Stein, MD, PhD, who is Assistant Professor at NYU School of Medicine and Associate Director of the Pigmented Lesion Service in the Ronald O. Perelman Department of Dermatology, NYU School of Medicine in New York, about how to differentiate atypical moles from melanoma.

PracticeUpdate: Dr. Stein, would you talk about the unusual nevi that are not malignant or premalignant?

Dr. Stein: Dysplastic nevi, or atypical moles, are very common. These moles are somewhat controversial because they have some of the features seen in a melanoma. It can be very difficult for both the patient and even the dermatologist to tell the difference between an atypical mole and an actual melanoma. But, we know that the vast majority of these moles are very stable and do not cause any harm.
Features that make moles look atypical can be size; some atypical nevi can be very large. Some moles may have more than one color, and some have a darker or lighter spot within them. These features can concern the patient and can concern the dermatologist as well because they can also be seen in a melanoma. However, by recognizing some of the features common in atypical nevi, you can reassure the patient that these atypical nevi are benign and do not need to be biopsied. Now, an important fact about atypical nevi is that they are a marker in a patient for a higher risk for melanoma. That doesn’t mean that the individual mole is more likely to turn into a melanoma, just that a patient who has atypical nevi is more likely to have a melanoma.

PracticeUpdate: How do you differentiate these nevi from a melanoma?

Dr. Stein: When you’re looking at a patient who has atypical nevi, it is important always to step back and look at the whole patient and figure out what’s normal for that patient in front of you. Usually a particular patient has one type of mole (a signature nevus);1 for example, a patient’s moles may all be dark brown, or all pink, or all have a dark spot within them. By recognizing what is normal for that patient, you can figure out which mole is not normal. A mole that is an outlier or an ugly duckling—a mole that looks different from the rest—is the one that should catch your eye, and you are going to look at it more closely.

PracticeUpdate: How do you treat these atypical moles?

Dr. Stein: Since atypical moles are benign, they really don’t need treatment; the important thing, actually, is not to treat them. As I said, just because a mole is atypical, it doesn’t mean that it is premalignant. Although that’s quite controversial, there is really no evidence that, because a mole looks atypical and because it has some features of a melanoma, it is on the verge of turning into a melanoma. And this can be really confusing for patients at times because premalignant lesions do occur on the skin. For example, we know that actinic keratoses certainly can turn into squamous cell carcinoma. However, it does not appear that there is the same association between dysplastic nevi, or atypical moles, and melanoma.
Because dysplastic nevi, or atypical moles, are not inherently premalignant lesions, they don't need to be removed for fear that they may turn into a melanoma. Only biopsy a mole that is atypical if you are actually suspicious that it may be a melanoma.

PracticeUpdate: What else is important for practicing dermatologists to know about this topic?

Dr. Stein: Patients who have a lot of moles, and a lot of atypical moles, can be difficult to care for because, one, they are at higher risk for melanoma, and you certainly don’t want to miss a melanoma; and, two, it can be difficult to examine their skin because it can be tricky to distinguish between atypical moles and a real melanoma.
There are tools that you can use in the clinical exam of patients with lots of moles and atypical moles. When there are many moles that you are concerned about, one thing you can do is take photos of the moles and then look at them over time to see if they are changing. Usually a melanoma changes over time, whereas a benign lesion, like an atypical nevus, is pretty stable. So, change can be an important sign of an early subtle melanoma. Dermoscopy is another way to get more information about a concerning mole to tell if there are any features worrisome for melanoma. I think dermoscopy is an important part of a good clinical exam of the patient with atypical moles because it can help minimize unnecessary biopsies and help detect subtle melanomas.

  • References
    1. Suh K-Y, JL Bolognia JL. Signature nevi. J Am Acad Dermatol. 2009;60(3):508-514.