By Marilynn Larkin
NEW YORK (Reuters Health) - Mild and moderate dysplastic nevi with microscopically positive margins but no residual lesion can be safely managed by observation, rather than re-excision, say California-based researchers.
"Dysplastic nevi are frequently re-excised following initial biopsy due to concerns for malignant transformation; however, the long-term risk of melanoma developing in mildly or moderately dysplastic nevi with positive histologic margins is unknown," Dr. Susan Swetter of Stanford Medicine and the VA Palo Alto Health Care System told Reuters Health by email.
To investigate, Dr. Swetter and colleagues examined records of patients with biopsy-confirmed dysplastic nevi with positive histologic margins who were diagnosed from May 1991 to July 2015, and who were followed up through May 2016.
As reported in JAMA Dermatology, online August 17, 498 patients (90% male) with positive-margin dysplastic nevi were included in the study. Overall, 191 nevi were re-excised and 399 were observed.
Followup data were available for an average of 5.5 years for 170 of the re-excised and 304 of the observed nevi. The team found that dysplastic nevi in the observation group were more likely to recur than those that were re-excised (3.3% versus 0%).
Two percent of the observed dysplastic nevi subsequently developed melanoma at the same site, compared with 0.06% of those that were re-excised.
In addition, five of the six observed patients who developed melanoma initially underwent partial biopsies that left grossly positive margins. One melanoma in situ evolved five years after excision of a biopsied moderately dysplastic nevus.
The team found only one case of thin invasive melanoma that measured one millimeter or less. No deaths from melanoma occurred due to transformation of biopsy-proven dysplastic nevi through the latest followup.
By contrast, new primary melanoma developed at other sites in 9.9% of cases of excised dysplastic nevi and 9.4% of resected dysplastic nevi.
"It is time to dispel longheld notions regarding the 'premalignant' status of the majority of (atypical nevi and dysplastic nevi), which more accurately serve as risk markers for melanoma development," the authors conclude.
Dr. Swetter emphasized, "Our study demonstrated less than a 2% risk of melanoma developing in transected dysplastic nevi (6/304) that were clinically observed for up to 20 years, most (5/6) of which were melanomas in situ and resulted from partial biopsy of the initial nevus, suggesting sampling error at the outset."
She concluded, "Our study supports that the threshold can be raised for re-excision of mildly to moderately dysplastic nevi that were biopsied with excisional intent."
Dr. David Fisher, director of the Cutaneous Biology Research Center at Massachusetts General Hospital in Boston, commented, "The authors' evidence supporting observation without reflexive re-excision is compelling, with several caveats, most of which are appropriately highlighted by the authors themselves."
"Consensus diagnostic criteria among dermatopathologists have been notoriously difficult to obtain. This will need to be carefully considered in applying the current results to broader populations," he told Reuters Health by email.
"Additionally, the current study included a largely male and high risk population. While this likely biased the study towards identification of recurrent/aggressive lesions, it is also possible that lesions arising at different anatomic sites, in females, and with other lower risk features, might display distinct recurrence features - such as a need for longer followup to assess local disease behaviors," Dr. Fisher observed.
"Still," he said, "the study is compelling and important, and provides a key data set to assist clinicians in conservative management of a significant population of patients with dysplastic nevi."
SOURCE: https://bit.ly/2bPhmhx
JAMA Dermatol 2016.
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