Growth into melanoma was detected in 4 patients (3.6%) at a mean interval of 44 months (median, 41 months; range, 13-79 months) (Table 4 and Figure 3). Of those patients with melanoma that showed growth, the mean age at presentation was 52 years (median, 53.5 years; range, 41-60 years), and no patient displayed autoimmune dysfunction, cutaneous melanoma, or ocular melanocytosis. One halo nevus was present in each patient, and quadrant location was inferior (n = 2), temporal (n = 1), or superior (n = 1). At presentation, the mean basal dimension was 6.8 mm (median, 6.75 mm; range, 5.5-8.0 mm) and the mean thickness was 2.2 mm (median, 2.2 mm; range, 2.0-2.5 mm), with proximity to the optic disc at a mean of 1.9 mm (median, 1.5 mm; range, 0-4.0 mm) and to the foveola at a mean of 2.6 mm (median, 1 mm; range, 1.0-7.5 mm). Associated features included subretinal fluid (n = 1), orange pigment (n = 1), and hollowness on ultrasonography (n = 3). Chronic features of drusen and retinal pigment epithelial changes were not present in any patient. In each patient, the halo encircled the nevus for all 12 clock hours, the width was 2 mm, and there was no change in halo over time. Two to 4 risk factors present were predictive of growth,11- 13 with a median number of 3.5 factors. In comparison, of the 106 halo nevi that showed no growth, the features included a mean basal dimension of 5.6 mm (median, 5.0 mm; range, 1.5-12.0 mm), a thickness of 1.5 mm (median, 1.6 mm; range, 1.5-3.3 mm), a proximity to the optic disc of 5.7 mm (median, 5.3 mm; range, 0-17.0 mm), a proximity to the foveola of 4.9 mm (median, 4.0 mm; range, 0-19.0 mm), subretinal fluid in 6 (5.7%), orange pigment in 8 (7.5%), hollowness on ultrasonography in 31 (29.2%), and related symptoms in 16 (15.1%).