Background: The dermatoscopic examination of the nail plate has been recently introduced for the evaluation of pigmented nail lesions. There is, however, no evidence that this technique improves diagnostic accuracy of in situ melanoma. Objective: To establish and validate patterns for intraoperative dermatoscopy of the nail matrix. Methods: Intraoperative nail matrix dermatoscopy was performed in 100 consecutive bands of longitudinal melanonychia that were excised and submitted to histopathologic examination. Results: We identified 4 dermatoscopic patterns: regular gray pattern (hypermelanosis), regular brown pattern (benign melanocytic hyperplasia), regular brown pattern with globules or blotch (melanocytic nevi), and irregular pattern (melanoma). Limitations: Nail matrix dermatoscopy is an invasive procedure that can not routinely be performed in all cases of melanonychia. Conclusion: The patterns described present high sensitivity and specificity for intraoperative differential diagnosis of pigmented nail lesions.
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