Baseline dermoscopic patterns predict long-term changes in nevus diameter and in dermoscopic features

Background: When monitoring melanocytic neoplasms, the pattern of change may distinguish nevi from melanoma. Anticipating the growth dynamics of nevi based on their dermoscopic pattern is important to make this distinction. Objective: The primary aim was to examine the association between nevus dermoscopic pattern at baseline and diameter change during long-term monitoring. The secondary aim was to examine the association between nevus dermoscopic pattern at baseline and changes in both dermoscopic pattern and colour during long-term monitoring. Methods: The study included high-risk adult patients that underwent ≥2 total-body photography (TBP) sessions, with at least 14 years' time gap between first and last sessions. Nevi on the torso, with available dermoscopic images, were included. New and disappearing nevi were defined as nevi not appearing on the first and last TBP, respectively. Nevus diameter and colour were assessed on clinical images of first and last TBP images. Dermoscopic images were analysed for dermoscopic patterns and structures at baseline and follow-up. Results: In total, 877 nevi from 101 patients were included. Mean follow-up time between TBPs and between dermoscopic images was 16.7 and 11.5 years, respectively. Most nevi were reticular or structureless at baseline, but new nevi had a higher frequency of peripheral globules and smudgy patterns. Peripheral globules and diffuse negative network patterns as well as regression structures were associated with nevus diameter growth. In total, 30% and 15% of new and existing nevi, respectively, demonstrated dermoscopic pattern change, mainly transforming into reticular and structureless patterns. Conclusions: Among high-risk patients, nevi showing peripheral globules or negative network are more likely to grow in diameter during long-term monitoring. Most nevi retain their overall dermoscopic pattern and those that change, mostly transform into reticular or structureless patterns.