Site-specific dermoscopic features of lip lentigines, distinctive from those of facial lentigines

Background: Lip lentigines are benign pigmentations often raising concerns to physicians and patients for fear of malignancy. Specific dermoscopic patterns of lip (mucosal) lentigines have not been clearly defined in the literature when compared to common facial (nonmucosal) lentigines. Objectives: This study aimed to define key dermoscopic features of lip lentigines to help diagnose these benign lesions more efficiently by calculating the specificity, sensitivity, and positive and negative predictive values (PPV and NPV) of dermoscopic patterns in lip and nonlip facial lentigines. Methods: A retrospective observational study was conducted at a medical center in Southern Taiwan. Dermoscopic images of 12 patients with lip lentigines and seven patients with 12 facial nonlip lentigines were inspected. Pattern recognition was performed via blind review by three clinicians. Dermoscopic images were assessed side by side with 12 published dermoscopic patterns of pigmented lesions, to see whether the patterns were presented. Results: Four dermoscopic patterns (hyphal, overlapping vessels, parallel lines, and fish-scale-like) showed very high specificity and PPV (all 100%) in lip lentigines when compared to facial nonlip lentigines. The sensitivity of these four patterns was 83%, 83%, 67%, and 58% and their NPV was 86%, 86%, 75%, and 71%, accordingly. Interrater consistency analysis from pattern recognition showed good consistency (Cronbach's alpha = 0.814) among reviewers. Conclusion: Hyphal, overlapping vessels, parallel lines, and fish-scale-like patterns are specific and sensitive dermoscopic patterns of lip lentigines when compared to facial nonlip lentigines. This knowledge of site-specific dermoscopic patterns could be used in characterizing benign and malignant pigmented lesions of the lip in future studies.