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Abstract

Graphite tattoo is a potential consequence from injury with a graphite-containing pencil and may be confused clinically for melanocytic lesions or other pigmentary disorders. A clear history of trauma will raise the possibility of this diagnosis. These lesions have been described clinically on other areas of skin as small blue-gray macules, but the size and shape is variable. Often history of a pencil injury is well established, so known lesions are not sampled. As a result, histopathologic findings are infrequently described, and to our knowledge, have never been documented in the nail unit. We report a 77-year-old female with an irregular subungual area of blue-gray pigmentation of her finger. She reported a pencil injury seventy years prior that resulted in a stable blue-gray macule, however the lesion began evolving in size, shape, color, and developed tenderness in the past year. Considering the changes, the clinical and onychoscopic findings inserted a chromonychia including a subungual blue nevus or other melanocytic lesion into the differential. A nail unit biopsy was performed because of evolving features. Histopathology demonstrated dense collections of variably-sized, darkly pigmented, polarizable material scattered throughout the dermis forming a nodular configuration with associated thickened collagen. This area visualized histopathologically correlated to a sphere-shaped object identified during biopsy.  A Prussian blue stain for iron was negative. The morphologic findings were consistent with graphite tattoo. Herein we emphasize the importance of clinicopathologic correlation in cases of subungual pigmentation of uncertain etiology, as well as novel histopathologic and clinicopathologic aspects of this entity.