Dendritic cells in reflectance confocal microscopy are a clue for early melanoma diagnosis in extrafacial flat pigmented melanocytic lesions

Differential diagnosis of extrafacial flat pigmented lesions with dermoscopic reticular and/or homogeneous pattern is challenging. Dendritic cells upon reflectance confocal microscopy (RCM) still represent a pitfall. This study aims to determine the role of dendritic cells upon RCM in the epidermis and dermo‐epidermal junction (DEJ), together with common RCM features for melanoma and nevi, in dermoscopically equivocal extrafacial flat pigmented lesions. A retrospective evaluation of RCM images of melanocytic extrafacial flat pigmented lesions with reticular and/or homogeneous dermoscopic pattern and with histopathological diagnosis, was performed. A multivariate model of RCM features was used to obtain a score of independent risk factors. A total of 698 lesions were included. Increasing patient age, epidermal dendritic cells, many dendritic cells in the DEJ (>30%) and many (>5/mm(2)) round atypical cells were independent risk factors for melanoma. Edged papillae and melanophages were indicative of nevus. A score based on these features was developed to assist in melanoma differential diagnosis. The RCM observation of abundant (>30%) dendritic cells in the DEJ is highly suggestive of malignity. This independent risk factor should also be considered for improved differential diagnosis of extrafacial melanoma.