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Summary

Background  Although dermoscopy of the nail plate is helpful to discriminate between benign and malignant causes of nail pigmentations, there remain ambiguous cases in which a matricial biopsy is required. When a subungual melanoma is diagnosed histopathologically, a complementary surgical treatment is performed secondarily, the duration of postoperative disability being accordingly prolongated.

Objectives  The purpose of our study was to evaluate the feasibility of an intraoperative diagnosis by reflectance confocal microscopy (RCM).

Patients and methods  Our series included nine consecutive patients who underwent a matricial biopsy for an acquired melanonychia (one benign lentigo and eight melanomas). RCM examination was performed in vivo on the nail matrix after reclination of the nail plate, and/or ex vivo on the fresh tissue biopsy. RCM data were compared with histopathology.

Results  There was a good correlation between confocal and histopathological features. Seven melanoma cases were unequivocally diagnosed intraoperatively according to the confocal features, whereas the lentigo was correctly classified as a benign lesion according to RCM. The remaining lesion could not be unequivocally classified by RCM and corresponded histopathologically to an early melanoma that required immunostaining to be diagnosed.

Conclusions  Intraoperative RCM examination of the nail matrix is an efficient diagnostic approach of melanonychia striata that permits an extemporaneous diagnosis of malignancy and therefore a one-step surgical treatment of in situ or minimally invasive melanoma, reducing dramatically the duration of postoperative disability.