Dermoscopic predictors of melanoma in small diameter melanocytic lesions (mini-melanoma): a retrospective multicentric study of 269 cases

Background: Incidence of cutaneous melanoma is steadily growing, and its early recognition is of paramount importance. Small, pigmented lesions often represent a challenge for the clinician, as predictors of melanoma have not yet been uniquely identified in this setting. Objectives: To identify dermoscopic features that aid in distinguishing small diameter melanomas (≤5 mm) from equivocal melanocytic nevi measuring ≤5 mm. Methods: A retrospective multicenter study was conducted to collect demographics, clinical and dermoscopic pictures of (i) histology-proven flat melanomas, measuring ≤5 mm, (ii) histology-proven but clinically/dermoscopically equivocal melanocytic nevi measuring ≤5 mm, and (iii) histology-proven flat melanomas, measuring >5 mm. An independent dermoscopic evaluation was performed. Differences in predefined dermoscopic features were assessed across the three groups. Results: A total of 103 melanomas measuring ≤5 mm were collected; 166 control lesions, comprising 85 large (>5 mm) melanomas and 81 dubious, clinically equivocal melanocytic nevi measuring ≤5 mm were included. Of the 103 mini-melanomas, only 44 were melanoma in situ. Five dermoscopic predictors of melanoma were identified for the assessment of flat, non-facial melanocytic lesions measuring ≤5 mm, namely: atypical pigment network, blue-white veil, pseudopods, peripheral radial streaks, and presence of more than one color. The latter were combined into a predictive model capable of identifying melanoma with 65% sensitivity and 86.4% specificity, at a cut-off score of 3. Among melanomas measuring ≤5 mm, presence of a blue-white veil (P = 0.0027) or negative pigment network (P = 0.0063) was associated with invasiveness. Conclusion: A set of five dermoscopic predictors of melanoma, atypical pigment network, blue-white veil, pseudopods, peripheral radial streaks, and presence of more than one color is proposed for the assessment of flat, non-facial melanocytic lesions measuring ≤5 mm.