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Reflectance confocal microscopy for the diagnosis of tinea nigra

Tinea nigra is an uncommon superficial mycosis caused by the darkly pigmented yeast Hortaea werneckii. It occurs mainly in tropical areas. Outside endemic regions its features may be less immediately recognized, and clinical confusion with melanocytic lesions may be possible. A 23-year-old woman presented with a 1-year history of a slow-growing, asymptomatic macule on her left sole. Physical examination revealed an irregular, slightly scaly, brown macule, with a maximum diameter of 10 mm (Fig. 1a). Clinical differential diagnoses included atypical naevus versus acral melanoma. Dermoscopy disclosed multiple, homogeneously arranged thin strands of brown dots or granules and short lines similar to spicules, which did not follow any furrow or ridge pattern (Fig. 1b). Further reflectance confocal microscopy (RCM) examination (VivaScope1500 , Caliber Imaging and Diagnostics, Rochester, NY, USA) was performed. Multiple elongated and round bright structures were seen at the stratum corneum, possibly corresponding to filamentous septate hyphae and arthroconidia, respectively. The remaining tissue up to the superficial dermis was remarkable for the absence of inflammation (Fig. 1c–f). In addition, no pagetoid cells, clusters/nests of melanocytes or atypical cells were observed. Therefore, the diagnosis