Melanoma risk in individuals with clinically atypical nevi

A lack of consensus as to the clinical and histologic characteristics of dysplastic nevi has resulted in the recommendation to abandon the term dysplastic nevus for the more descriptive atypical nevus or atypical mole. The significance of the presence of one or more such lesions, histologic features notwithstanding, has not been carefully examined. The risk of melanoma was assessed in individuals with atypical nevi monitored regularly in our Pigmented Lesion Clinic. Any patient enrolled in this subspecialty clinic between 1980 and 1985 without the diagnosis of melanoma who had at least one sufficiently atypical-appearing nevus and who was followed up for a minimum of 5 years was entered in the study.

A total of 155 such individuals were identified. The mean (+/- SEM) age of the patients at first evaluation was 26 +/- 1 years. The group was followed for 7 +/- 1 years. The male-female ratio was 1:1. A family history of melanoma was present in 71 subjects (46%). Of the 155 patients, two developed melanoma. The thickness of the tumors in both patients was less than or equal to 0.8 mm. Twenty-five patients (16%), including the two with melanoma, had at least one nevus removed that showed "severe nuclear atypia."

The risk of melanoma in individuals with atypical nevi is significantly greater than expected. The elevated risk was demonstrated even though careful, regular evaluations and removal of more atypical lesions were performed. This study provides evidence that, compared with no surveillance, the meticulous monitoring of patients with clinically atypical nevi is more likely to result in the detection of melanoma at thin stages, with an attendant improved prognosis.