Reflectance confocal microscopy of mucosal pigmented macules: a review of 56 cases including 10 macular melanomas

Background Although most mucosal pigmented macules are benign, it can be clinically challenging to rule out an early melanoma. Reflectance confocal microscopy (RCM) is a noninvasive imaging technique useful in discriminating between benign and malignant skin lesions. Objectives To describe the confocal aspects of benign and malignant mucosal pigmented macules with histopathological correlations. Methods We retrospectively reviewed the confocal images of 56 labial or genital pigmented macules including 10 macular melanomas. According to the retrospective nature of the study, we evaluated the recorded images chosen by the physicians that performed the RCM examination for each case. Results In benign macules, the most frequently observed pattern was a ringed pattern characterized by round or polycyclic papillae, with a hyper-reflective basal layer; another pattern was characterized by sparse bright dendritic cells in the basal layer, the basal epithelial cells being otherwise less reflective. Roundish cells, a high density of dendritic cells with atypias and intraepithelial bright cells were clues to the presence of malignancy. Conclusions Reflectance confocal microscopy seems to be a valuable tool to noninvasively differentiate benign from malignant mucosal pigmented macules and target biopsies in cases of equivocal features.