In general, pigmented macrophages are an incidental finding on biopsy and resection specimens of the small intestine and are not necessarily pathologic. The differential diagnosis for the etiology of pigment includes: laxatives (specifically anthraquinones), as well as natural laxatives such as rhubarb, senna, frangula, and aloe vera. Brown bowel syndrome (malabsorption of vitamin E and fat), hemosiderin, ink, melanin, and barium granuloma are further considerations. In the liver, macrophages can contain ceroid pigment (from cellular degeneration) and bile pigment. Other pigments found in the liver include iron pigment, lipofuscin pigment, copper pigment, and bile, although these are generally found in hepatocytes.
In this case, the dark brown-black pigment in the ileum is consistent with ingestion of titanium dioxide, commonly found in toothpaste. Titanium dioxide, aluminosilicates and mixed environmental silicates are collectively referred to as "atmospheric dust" and are not clinically significant, but should be distinguished from the pathologic entities listed above.
See Related Content for references:
1) Iacobuzio-Donahue C, et al. Gastrointestinal and Liver Pathology: A Volume in the Series Foundations in Diagnostic Pathology. Elsevier Inc., 2005.
2) Sagaert X, et al. Virchows Arch. 2012 Jun;460(6):555-67.
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