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Case of subungual tumoral melanosis: The detection of melanoma cells and dermoscopic features

Dear Editor, Tumoral melanosis is a rare event, which substitutes melanin-laden macrophages (melanophages) for most melanoma cells. Although dermoscopic features of pigmented epithelioid melanocytoma and tumoral melanosis share black and blue homogenous areas, black streaks and crystalline structures may lack in tumoral melanosis. No detailed presentation of the dermoscopic features of subungual tumoral melanosis has been published to date. Here, we present a case of subungual tumoral melanosis. We emphasize the crucial importance of detecting residual melanoma cells using dermoscopy for the diagnosis of tumoral melanosis. A 67-year-old woman presented with a black tumor under the nail plate of her right thumb. The patient had initially recognized black streaks at the nail 5 years before. Those black streaks had gradually enlarged 2 years before. Physical examination revealed a 5 mm 9 10 mm black tumor under the nail plate of her right thumb. The nail plate was partially destructed and dented. A slight pigment macule was recognized at the lateral and distal periungual skin (Fig. 1a). Dermoscopy revealed a blue whitish veil on black homogenous areas with surface scales. A slight bleeding was found at the lateral portion of the black tumor (Fig. 1b). At the distal periungual skin, a parallel ridge pattern was found (Fig. 1c). The diagnosis of subungual melanoma was suspected. Her right thumb was amputated and a sentinel lymph node biopsy was performed due to the potential presence of melanoma cells in the black tumor mass. Histopathological examination revealed a massive infiltrate of melanophages under a large cleft of the