Dermoscopic and confocal features of an axillary “special site” nevus

"Nevi of special sites" is a term that denotes melanocytic nevi presenting in specific anatomic locations including the scalp, genital area, flexural sites, and acral sites [1]. Nevi from these anatomic sites display at times histopathologic features that may lead the reading pathologist to recommend re-excision of these benign nevi. Reflectance confocal microscopy (RCM) is a noninvasive imaging tool that allows for visualization of epidermal, dermal-epidermal junctional (DEJ), and superficial dermal tissue structures at cellular level resolution. RCM features of special site nevi have not been previously described in the literature. Defining the RCM characteristics of special site nevi may increase diagnostic accuracy and assist in ruling out melanoma. Here, we report a case of a pigmented lesion appearing in the axilla of a patient with a recently diagnosed melanoma. Dermoscopic and histopathologic results were consistent with the diagnosis of nevus in flexural anatomic sites. In this case, RCM showed a regular honeycomb pattern of epidermal keratinocytes and enlarged, non-homogenous, discohesive nests at the DEJ, a pattern that corresponded well with the histopathologic findings. Larger studies are needed to establish RCM features of special site nevi in order to reliably rule out melanoma and lower the rate of unnecessary excisions of these benign nevi.