A 60-year-old woman presented with a pigmented lesion on the upper left gingival mucosa of 2 years duration. The lesion was in an area where a dental metallic prosthesis had been inserted into a nearby tooth several years earlier. A biopsy of the affected mucosa showed aggregates of pigmented granules varying in size in the dermis, extracellular matrix and within macrophages; these did not stain with melanin stains. The diagnosis was consistent with an amalgam tattoo.