Anatomic Transitions and the Histopathologic Features of Melanocytic Nevi

In their letter, Braun et al¹ reported a case of an acral melanocytic lesion that exhibited a completely benign dermoscopic pattern but was histopathologically diagnosed as melanoma in situ. As previously noted,² despite benign clinical features, melanocytic nevi located in transition sites between glabrous and nonglabrous skin and in interdigital areas often histopathologically exhibit a random, irregular distribution of melanocytes as solitary units and in nests within the epidermis (Figure). The lesion described by Braun et al¹ may be such a case. At first, we diagnosed these cases as malignant melanoma. Later, we noticed that most of melanocytic lesions affecting these anatomic sites showed a random, irregular distribution of melanocytes as solitary units and in nests within the epidermis. Noteworthy is that most patients with this presentation were young, ranging in age from 10 to 30 years. Malignant melanomas on acral skin mostly affect older persons. Furthermore, most of the lesions were clinically benign: small and regular in color (unpublished data, 2007), though some were larger, as in the case reported by Braun et al.¹ These findings prompted us to consider that these lesions were not melanomas but rather melanocytic nevi. And now we believe that most melanocytic nevi located on the transition areas show histopathologic features mimicking those of malignant melanoma.