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With a median follow-up of 5.5 years, only six melanomas have been identified (one in situ) at the site of previous biopsy, which was not statistically significantly different from the re-excised control group. Five of six recurrences were in patients with grossly positive margins. The researchers therefore concluded that for patients with DN with mild-to-moderate dysplasia, there is no need for additional re-excision if positive, microscopic margins are identified. The team does recommend re-excision if the nevus was not completely resected due to a risk for sampling error and possibly missing a diagnosis of melanoma. This confirms previous observations that the presence of DN correlates with an increased risk of developing new primary melanoma and that these patients should be screened accordingly.
Although the study involved a retrospective cohort with a low rate of development of site-specific melanoma, one can consider not recommending re-excision for patients with small microscopic positive margins. As most recurrences in the experimental group happened in patients who had grossly positive margins, re-excision in those cases should be considered if technically feasible. More importantly, identifying DN increases the patient's chances of developing melanoma in his or her lifetime, and these patients should undergo routine screening going forward.
Dysplastic nevi (DN) are frequently re-excised following initial biopsy due to concerns about malignant transformation. The long-term risk of melanoma developing in mildly or moderately DN with positive histologic margins has been unknown. According to the results of a new , however, patients with mild or moderate DN with microscopically positive margins and no concerning clinical residual lesion can be safely observed rather than having to undergo re-excision.
"Our findings add to recent data suggesting that re-excision of mild to moderate DN is generally not warranted in the absence of severe dysplasia or a non-representative biopsy," said , of Stanford University Medical Center and Canter Institute and VA Palo Alto Health Care System.
In the retrospective cohort study, Swetter and colleagues used a consecutive sample of 1,473 histologically confirmed DN to identify 590 cases of DN in 498 patients, with a mean age of 58, who were followed for more than 20 years. Six cases of melanoma (five in situ) arose in the 304 cases with positive margins that were clinically observed, only one of which developed from an excisionally biopsied dysplastic nevus. One melanoma in situ arose in the 170 patients who underwent complete excision at the outset.
Among the 590 positive-margin DN, 191 were re-excised and 399 were clinically observed without further surgery. DN in the clinically observed group were more likely to recur (3.3%) than those that were re-excised (0%). Some 2% of the observed DN subsequently developed melanoma at the same site as compared with 0.06% of those that were re-excised.
Only one case of thin invasive melanoma (1 mm or less) was observed, and no deaths from melanoma arising from biopsy-proven DN occurred through the latest dermatology follow-up.
New primary melanoma developed at other sites in 9.9% of excised and 9.4% of resected DN.
The presence of atypical nevi or histologic DN is an established risk factor for melanoma, but the rates of nevus-associated melanoma appear to be low -- in the 20% range -- Swetter noted. She told ľֱ that she discourages partial biopsies of pigmented lesions suspicious for melanoma: "Partial biopsy of a concerning nevus should be discouraged, as sampling error may result in a later diagnosis of melanoma. Excisional biopsy with the saucerization/deep shave technique resulted in optimal histologic assessment of DN in our study."
Some clinicians still believe in the premalignant status of the majority of atypical nevi and DN, but "our long-term analysis demonstrating favorable long-term outcomes for patients with incompletely excised DN adds to recent publications suggesting that these lesions may be safely observed when severe dysplasia is not present on attempted excisional biopsy," she said.
The cost of unnecessary re-excisions of DN to both patients and the health system is mounting, Swetter continued. "It is time to dispel long-held notions regarding the 'precursor' status of the majority of DNs, which more accurately serve as risk markers for melanoma development. Clinically stable, dermoscopically banal-appearing atypical nevi can generally be monitored without biopsy."
The team also observed that melanoma risk at other sites of the body remains elevated in the patients with DN. "Regular dermatologic follow-up of patients with clinical atypical nevi is warranted for early detection of severe DN and primary melanoma," said Swetter, adding that there are no data to support increased surveillance in females over men with atypical nevi, or that DN in certain anatomic sites are at increased risk of malignant transformation.
The proportion of DN or other nevus subtypes that remains unknown, the researchers noted.
They also acknowledged that the study cohort represented a high-risk group, composed largely of older men with substantial sun exposure or patients with an atypical mole phenotype. One quarter of the participants had a prior melanoma. This is consistent with showing up to a 20-fold increased risk of melanoma in patients with atypical nevi or DN. Patients with additional risk factors need long-term dermatologic surveillance, Swetter said.
In conclusion, she stated: "Our study supports that the threshold for re-excision of mildly to moderately DN can be raised."
Swetter had no disclosures.
Primary Source
JAMA Dermatology
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