Noninvasive RCM for Differentiation of Melanotic Macules From Melanocytic Lesions-Blinded Evaluation of a Series of 42 Pigmented Macules

BACKGROUND Differentiation of melanotic macules from melanocytic lesions, most importantly of melanoma, is a common problem on clinical-dermoscopic examination. OBJECTIVE To assess the value of noninvasive reflectance confocal microscopy (RCM) in the differential diagnosis of melanotic macules and melanocytic lesions. PATIENTS AND METHODS Reflectance confocal microscopy images of 42 pigmented macules on mucocutaneous junctions of genitalia and lips, including 31 melanotic macules, 6 nevi, and 5 melanomas, were retrospectively and independently assessed in a blinded manner by one expert observer and 2 less experienced observers together. RESULTS The authors differentiated 3 subtypes of melanotic macules; 2 subtypes ("solar lentigo type" and regular subtype of "dendritic type" melanotic macules) could be classified with confidence as benign by all RCM investigators, comprising 64% of melanotic macules. The third subtype (irregular subtype of "dendritic type" melanotic macules; 36%) displaying RCM features overlapping with melanoma was difficult to differentiate and should be biopsied not to miss a melanoma. The RCM differentiation between melanotic macules and nevi was easily performed. CONCLUSION RCM has the potential to increase the diagnostic accuracy in the noninvasive differentiation of pigmented macules on mucocutaneous junctions.