Amalgam pigmentation (amalgam tattoo) of the oral mucosa. A clinicopathologic study of 268 cases.

A series of 268 cases of amalgam tattoo is analyzed both clinically and histologically. The most common location was the gingiva and alveolar mucosa, followed by the buccal mucosa. Histologically, the amalgam was present in the tissues as discrete, fine, dark granules and as irregular solid fragments. The dark granules were arranged mainly along collagen bundles and around blood vessels. They were also associated with the walls of blood vessels, nerve sheaths, elastic fibers, basement membranes of mucosal epithelium, striated muscle fibers, and acini of minor salivary glands. Dark granules were also present intracellularly within macrophages, multinucleated giant cells, endothelial cells, and fibroblasts. Although in 45% of the cases there was no tissue reaction to the amalgam, in 17% there was a macrophagic reaction and in 38% there was a chronic inflammatory response, usually in the form of a foreign body granuloma, with multinucleated giant cells of the foreign body and Langhans types. Asteroid bodies were also found in some of the foreign body giant cells.