Asbestosis is defined as diffuse interstitial fibrosis of the lung that has been caused by inhalation of asbestos fibers. Clinically evident and radiologic changes of asbestosis are usually associated with prolonged heavy exposures to asbestos, which are far higher than necessary
to produce mesothelioma. Changes of asbestosis are frequently absent in cases of mesothelioma. If they are present, then there is usually a strong and convincing history of asbestos exposure.
The main histopathologic evidence for asbestos exposure is dependent on the finding of asbestos bodies in light microscopic sections of lung tissue either by conventional or iron stains. Asbestos bodies are golden, brown, club-shaped, often beaded structures that contain a clear pale transparent straight needle-like core. They are formed by the coating of the asbestos fiber with ferritin and protein and take months or years to develop after deposition of the fiber in the lung. If the morphologic criteria are carefully adhered to the majority (greater then 95%) of the
asbestos bodies are found on examination by electron microscopy with energy dispersive x-ray spectrometry to contain commercial amphibole (crocidolite or amosite) cores. In some areas of the world with environmental exposures to asbestos they contain tremolite or anthophyllite. Asbestos bodies formed from chrysotile are rare. The finding of one convincing asbestos body by light microscopy in a standard histologic section nearly always signifies an above-background exposure. However, ferruginous bodies that are not formed on asbestos fibers can
occur, for example, on talc, mica, kaolin, coal, carbon, rutile, and iron. These are distinguished by having cores that are yellow or black or platy rather than fibrous. Particular care has to be exercised by the histopathologist when evaluating cases with mixed dust exposures where substantial amounts of sheet silicates (talc, mica, kaolin, etc.) are present; these silicates can be coated to form ferruginous bodies and although these are platy, they can be cut at such an angle as to appear to be fibrous and can be incorrectly identified as asbestos. If the histopathologist finds clusters of asbestos bodies, this usually signifies very high levels of commercial asbestos fibers.
to produce mesothelioma. Changes of asbestosis are frequently absent in cases of mesothelioma. If they are present, then there is usually a strong and convincing history of asbestos exposure.
The main histopathologic evidence for asbestos exposure is dependent on the finding of asbestos bodies in light microscopic sections of lung tissue either by conventional or iron stains. Asbestos bodies are golden, brown, club-shaped, often beaded structures that contain a clear pale transparent straight needle-like core. They are formed by the coating of the asbestos fiber with ferritin and protein and take months or years to develop after deposition of the fiber in the lung. If the morphologic criteria are carefully adhered to the majority (greater then 95%) of the
asbestos bodies are found on examination by electron microscopy with energy dispersive x-ray spectrometry to contain commercial amphibole (crocidolite or amosite) cores. In some areas of the world with environmental exposures to asbestos they contain tremolite or anthophyllite. Asbestos bodies formed from chrysotile are rare. The finding of one convincing asbestos body by light microscopy in a standard histologic section nearly always signifies an above-background exposure. However, ferruginous bodies that are not formed on asbestos fibers can
occur, for example, on talc, mica, kaolin, coal, carbon, rutile, and iron. These are distinguished by having cores that are yellow or black or platy rather than fibrous. Particular care has to be exercised by the histopathologist when evaluating cases with mixed dust exposures where substantial amounts of sheet silicates (talc, mica, kaolin, etc.) are present; these silicates can be coated to form ferruginous bodies and although these are platy, they can be cut at such an angle as to appear to be fibrous and can be incorrectly identified as asbestos. If the histopathologist finds clusters of asbestos bodies, this usually signifies very high levels of commercial asbestos fibers.
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