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No melanomas developed at sites of incompletely excised histologically dysplastic nevi

No patients developed melanoma at the site of a histologically dysplastic nevus that approached a microscopic border but was not re-excised during long-term follow-up, according to study results.

Researchers conducted a retrospective study of 115 patients who were evaluated in the dermatology department at Mayo Clinic, Rochester, Minn., from 1980 through 1989 and had a histologically dysplastic nevus (HDN) excised. The HDN “extended to within 0.2 mm of a microscopic punch, shave or excision border and was not re-excised,” the researchers reported.

Of the nevi, 66 were mildly dysplastic; 42, moderately dysplastic; and seven, severely dysplastic. The most common location of the nevi was the trunk. Punch technique was used primarily for HDN removal (69.7%), followed by shave (19.1%) and elliptical excision (11.3%).

Average follow-up was 17.4 years, with 71.3% of patients followed longer than 10 years; 67.8%, longer than 15 years; and 63.4%, longer than 20 years. There were no metastatic melanomas observed during follow-up, and none of the HDNs that approached a microscopic border advanced to melanoma.

Researchers said the study was limited because it was retrospective and confined to one large academic medical center.

“During a long-term follow-up period, no patient developed melanoma at the site of an incompletely or narrowly removed HDN, providing evidence that routine re-excision of mildly or moderately dysplastic nevi may not be necessary,” the researchers concluded. “Avoiding re-excision of these nevi encountered in daily practice would result in fewer surgical procedures, with associated decreases in morbidity, including cosmetic disfigurement, and health care utilization and costs.”