EXPERT ANALYSIS FROM PDA 2015
PARK CITY, UTAH (FRONTLINE MEDICAL NEWS) – When you ask clinicians why they elect to reexcise dysplastic nevi, you’re likely to get a variety of answers, according to Dr. Douglas Grossman.
“Sometimes they have no reason all,” Dr. Grossman, professor of dermatology at the University of Utah, Salt Lake City, said at the annual meeting of the Pacific Dermatologic Association. “Sometimes the answer is ‘to prevent recurrence.’ Sometimes it’s to ensure complete removal of the lesion, to confirm the diagnosis, to rule out melanoma, or for ‘therapeutic’ purposes.”
Dysplastic nevus margins are often positive, “because the melanocytes in these lesions tend to extend up to 2 mm beyond clinical margins,” Dr. Grossman said. “I always try to remove the entire clinical lesion as well as 1-2 mm around the lesion to avoid positive margins.”
A survey of 101 Chicago Dermatological Society members found wide variation in clinical practice concerning how clinicians manage dysplastic nevi if the margins are clear vs. positive, and based on the degree of atypia ( Arch Dermatol. 2012;148[2]:259-60 ). The greatest quantitative shift in decision making (from observe to reexcise) was seen for dysplastic nevi with moderate dysplasia. Specifically, the decision to reexcise dysplastic nevi with moderate dysplasia ranged from 9% (for clear margins) to 81% (for positive margins) of respondents. “The margin status is driving the management,” said Dr. Grossman, who was not involved with the study.
In his opinion, two “unspoken fears” are also impacting the way clinicians treat dysplastic nevi. The first is that the nevus will recur in the scar years later and be indistinguishable from melanoma – the so-called pseudomelanoma phenomenon. The second fear is that residual nevus cells left behind will transform to melanoma. Evidence for these two possibilities, however, is lacking, Dr. Grossman said. According to a large study of pseudomelanoma phenomena, recurrence was rare and easily distinguishable from cases of melanoma with regression ( Modern Pathol. 2009;22:611-7 ). “Almost all of them had recurred within a year, so if a nevus is going to recur, it’s usually going to recur within that first year,” he said.
As for the issue of recurrence, Dr. Grossman led a research team that evaluated 271 nevus biopsy sites in 115 patients ( J Am Acad Dermatol. 2010;62[4]:591-6 ). At greater than 2 years of follow-up they observed a recurrence rate of 3.6% for dysplastic nevi, compared with 3.3% for nondysplastic nevi, “which is similar,” he said. In terms of melanoma development, one study of 28 incompletely removed dysplastic nevi found that no melanomas developed during 5 years of follow-up ( Am J Dermatopathol. 1985;7 Suppl:93-7 ).
Dr. Grossman referenced four cases in the medical literature in which the diagnosis was changed upon reexcision from dysplastic nevus to melanoma. “The question here is whether the initial biopsy or the reexcision was the correct diagnosis,” he said. “Development of melanoma at the site of a previously biopsied dysplastic nevus is exceedingly rare, and has not been described beyond a few case reports. The most likely explanation for how this could occur would be sampling error. If you have a melanoma arising at the site, maybe it was melanoma to start with, and the diagnosis was missed on the original biopsy. It could also be the case of pseudomelanoma phenomenon where it’s a nevus to start with but it comes back looking more atypical, so it’s incorrectly diagnosed as melanoma. A final possibility, which is the least likely, is that the few nevus cells left behind transformed into melanoma.”
According to a recent consensus statement from the Pigmented Lesion Subcommittee of the Melanoma Prevention Working Group, mild/moderate dysplastic nevi with clear margins do not need reexcision ( JAMA Dermatol. 2015;151[2]:212-8 ). The working group also recommends that mild dysplastic nevi with positive margins may be safely observed and that observation for moderately dysplastic nevi with positive margins “may be a reasonable option.”
Dr. Grossman reported having no financial disclosures.
