The distribution of melanocytic naevi in melanoma patients and control subjects.

A study of 121 melanoma patients and 139 control subjects was conducted among whites to examine and compare the distribution of non-dysplastic and dysplastic naevi and other pigmented lesions in each group. Melanoma patients had a mean of 97 melanocytic naevi which were greater than 2 mm in diameter and controls had a mean of 36 such naevi, while the medians were 58 and 22 respectively (p less than 0.0001). 55% of melanoma patients and 17% of controls had at least one clinically determined dysplastic naevus, and 26% of melanoma patients and 6% of controls had at least 5 dysplastic naevi. Men were found to have more naevi on the trunk than women in both melanoma cases (p = 0.01), and controls (p = 0.005). Dysplastic naevi were most often found on the trunk and were present at this location in 51% of cases and 17% of controls. Melanoma patients and control subjects with dysplastic naevi, when compared to those without these lesions, had larger number of non-dysplastic naevi. Lentigines were more common among melanoma patients that among control subjects (p = 0.02). There were no differences in the number of non-dysplastic naevi among cases with light and dark hair and eyes, or among controls with these characteristics. There also was little variation in the number of naevi according to number of blistering sunburns.