Ferruginous bodies are commonly seen in:

Inorganic paicles may become coated with iron containing proteinaceous material, these bodies are called ferruginous bodies. They mimic asbestos bodies and can be seen in patient with asbestosis but is not specific hence asbestosis is the best answer. Ferruginous bodies are most commonly seen in Asbestosis. Ref: Robbin's Illustrated Pathology, 7th Edition, Page 736 ; Concise Pathology By Chandrasoma P, Taylor C, 3rd Edition, Page 541