Lung – Foreign Body
comment:The term "foreign body" can encompass the presence of a variety of environmental or aberrant material within the lung, such as accidentally inhaled bits of plant material representing bedding or feed ( Figure 1 , Figure 2 , Figure 3 , and Figure 4 ), hair ( Figure 5 , Figure 6 , and Figure 7 ), or corn oil vehicle related to gavage error ( Figure 8 ). If the morphology of the foreign material is consistent with the test agent, the material is seen only in exposed animals, and the amount of material correlates with the exposure concentration, the term "foreign material" should be used rather than foreign body. Hair shafts are translucent and multilayered. Corn oil ( Figure 8 ) consists of translucent, pale yellow, birefringent droplets. Feed or plant-based bedding can be identified by the presence of plant cell walls. The inhaled material typically incites a focal suppurative, granulomatous, or pyogranulomatous reaction and is usually surrounded by accumulations of macrophages and/or neutrophils. The reaction to corn oil can vary depending upon whether test material is present in the oil and type of test material. In a vehicle control animal, the reaction to corn oil may be limited and consist primarily of alveolar macrophages around the oil. Foreign bodies are typically sporadic findings with no correlation to exposure concentration. The accumulation of substantial amounts of particulate matter in the lung has been diagnosed as pneumoconiosis, but this term is considered outdated and generally not used.
recommendation:Lung - Foreign body should be diagnosed when present but should not be graded. The specific location (e.g., alveolus, bronchus, or bronchiole) should be indicated in the diagnosis as a site modifier. The inflammation (or histiocytic infiltration) that accompanies a foreign body should not be diagnosed separately unless warranted by severity. The term "foreign material" should be used when the material is thought to be the test agent based on morphology, correlation with exposure concentration, and presence only in exposed animals.
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