Answer: Image 6C. This structure (arrow) was found in the wall of a small airway. What is it? A ferruginous body, a non-specific term for a fiber that has been coated with an iron-protein coat in a macrophage that then disappears. This body with a thin, transparent core may represent an asbestos body in this man who probably had exposure to asbestos as a mechanic, but it could have another type of mineral core.

What is its significance? It signifies only past exposure to fibrous dust. In this man, the dose inhaled did not produce any dust-related disease.

Image 6

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