Dermatologists agree that the presence of dysplastic nevi represents a risk for the development of malignant melanoma. But that's where agreement may end. Opinions vary from believing the nevi themselves are premalignant, to having no malignant potential and everything in between. A leading dermatopathologist speaks on the issue.
Some view all dysplastic nevi as precursors to malignant melanoma, and believe that, therefore, they should be excised. Others believe dysplastic nevi may have potential to evolve into malignant melanoma, and still others believe none of these lesions will evolve into malignant melanoma, says Terry Barrett, M.D., a dermatopathologist, director of the division of dermatopathology at ProPath Laboratories in Dallas, and a clinical professor of dermatology and pathology at the University of Texas Southwestern School of Medicine, Dallas.
Moreover, there is a numerical relationship between the presence of these lesions and the risk for developing melanoma: the greater the number of dysplastic nevi, the greater the risk of developing melanoma.
"Having a dysplastic nevus means there is a strong association with the patient developing melanoma," Dr. Barrett says. "Patients with large numbers of dysplastic nevi have a much greater likelihood of developing melanoma than patients who don't have large numbers of dysplastic nevi."
Dysplastic nevus syndrome is also known by other names such as familial atypical mole melanoma syndrome. Patients with the syndrome typically have more than 50 nevi, and some have more than 100. The National Institutes of Health classified the dysplastic nevus as a nevus with architectural disorder. In addition, a dysplastic nevus has also been called a Clark's nevus, so named after the physician who first identified the lesions. Dermatopathologists do not have a consensus of how to classify these lesions on a dermatopathologist's report, Dr. Barrett tells Dermatology Times.
"For a long time, we didn't know the risk of melanoma related to the number of dysplastic nevi," Dr. Barrett says. "If you have one dysplastic nevus, your chance of having melanoma is about the same risk as a person who has red or blond hair. We know people with red or blond hair have slightly increased risk over a darker-skinned person. The bottom line is any dysplastic nevus is a powerful predictor of risk. The more dysplastic nevi you have, the greater your risk."
When the nevi present as part of familial atypical mole melanoma syndrome, one or more of a patient's parents had dysplastic nevi, Dr. Barrett explains.
"If patients do have this syndrome and their parents developed melanoma, the risk of the patient who has dysplastic nevi developing melanoma is higher still," Dr. Barrett says. "Their lifetime risk of developing malignant melanoma can approach 50 percent. It can be higher, up to 100 percent, if both parents had dysplastic nevi and later developed malignant melanoma."
Making the call
Dermatologists need to distinguish between dysplastic nevi and common-acquired nevi, and alert the patients and their other healthcare providers to the presence of dysplastic nevi, ensuring those patients are monitored very closely, Dr. Barrett adds.
"It's important to make the clinical and histologic diagnosis of a dysplastic nevus and separate it out from the other type of acquired nevus," Dr. Barrett says. "People with large numbers of common-acquired nevi are at increased risk for melanoma, but that increased risk is much less than those patients who have the dysplastic nevi type."
According to Dr. Barrett, dysplastic nevi are markers for disease, but are not themselves lesions that are potentially malignant melanoma.
"My own opinion is that the lesions are not precursor lesions to melanoma, but are powerful predictors of patients who are at increased risk for malignant melanoma," Dr. Barrett says. "It's a controversial topic, and many (clinicians) believe they are pre-malignant lesions and that not all, but some, lesions will evolve into melanoma over time. I am not convinced by the evidence we have that these nevi will evolve into melanoma."