Reduced Visibility of Pigment Network Under Sub‐UV Reflectance Dermatoscopy Compared to Polarised Dermatoscopy: A Novel Diagnostic Clue to Differentiate Melanomas From Nevi

ABSTRACT Background Melanoma accounts for more than 75% of skin cancer‐related mortality. Dermatoscopy is an evidence‐based technique for earlier detection, yet differentiating melanocytic lesions remains challenging. Sub‐UV reflectance dermatoscopy (sUVRD) uses purple light (405 nm) to visualise chromophore distribution in the skin. Objectives This study aimed to evaluate whether the visibility of pigment network in melanomas is reduced under sub‐UV reflectance dermatoscopy (sUVRD) compared to polarised dermatoscopy (PD), and to assess this as a potential diagnostic clue for malignancy in melanocytic lesions. Methods We retrospectively analysed routinely collected medical images of pathology‐confirmed non‐acral non‐facial melanomas and clinically/dermatoscopically typical nevi in consecutive adult patients seen at Centre Léon Berard from 13 July 2023 to 28 October 2024. Only quality images displaying a pigmented network in at least one quadrant in PD were included. Three blinded raters with varying dermatoscopic experience (10+, 5+, < 1 years) assessed whether pigment network visibility under sUVRD was reduced or equal compared to PD. Results Among 39 patients (M/F ratio 1.29), 20 melanomas and 20 nevi were analysed. Pigment network visibility under sUVRD was significantly more reduced in melanomas versus nevi (60% vs. 20%; Chi‐square p = 0.024; OR = 6; sensitivity 0.6; specificity 0.8; PPV 0.75; NPV 0.67; Fragility index 2). Inter‐rater concordance was moderate (Fleiss' kappa 0.41). Conclusions In this preliminary study, reduced pigment network visibility under sUVRD compared to PD showed promise as a clue to differentiate melanomas from nevi displaying dermatoscopic network, with an odds ratio superior to most common melanoma criteria. Further validation on larger datasets with pathology‐confirmed lesions and standardised imaging conditions is required.