AbstractBackgroundLine‐field confocal optical coherence tomography (LC‐OCT) is an emerging diagnostic tool with imaging depth reaching ~400 μm and a novel three‐dimensional (3D) cube providing cellular resolution. As far as we are aware, there are only a limited number of papers that have reported diagnostic criteria for melanocytic lesions using this technique, and none of them have been multicentric.ObjectivesOur aim was to establish the diagnostic criteria for melanocytic lesions using LC‐OCT and identify the most significant architectural and cytologic features associated with malignancy.MethodsA retrospective evaluation of 80 consecutive melanocytic lesions from a prospective multicentric data set spanning three European centres was conducted. We excluded facial, acral and mucosal lesions from the study. Dermoscopic and LC‐OCT images were evaluated by a consensus of four observers. Multivariate logistic regression with backward elimination was employed.ResultsThe main melanoma diagnostic criteria include detecting >10 pagetoid cells in 3D acquisition, irregular 3D epidermal architecture, disrupted dermoepidermal junction (DEJ) and clefting. Significant risk factors were irregular 3D epidermal architecture, >10 pagetoid cells, dendritic cells at DEJ without underlying inflammation. Novel malignancy criteria in vertical view were DEJ disruption and clefting around atypical melanocyte nests. Exclusive melanoma features were epidermal nests, epidermal consumption, dense dermal nests with atypia. Protective features in the absence of any malignancy indicators were DEJ ring pattern, cobblestone, elongated rete ridges (vertical), well‐defined DEJ and wave pattern (vertical).ConclusionsA series of diagnostic criteria for the identification of melanocytic lesions with LC‐OCT have been established. Validation of these criteria in clinical practice through future studies is essential to further establish their utility.