Asbestos-Related Lung Disease
Michael Lewin-Smith, M.B., B.S.
Allen P. Burke, M.D.
Types of Asbestos
Asbestos is a group of silicates that are defined by the formation of very long, thin fibers. Legally, there are six mineral types of “asbestos,” one in the serpentine group of magnesium silicates (chrysotile) and five in the amphibole group (amosite, anthophyllite, actinolite, tremolite, and crocidolite).1 The last three are noncommercial; sources of exposure for these include rock or gravel or contamination of other mineral mines. The elements (other than silicon) in the amphibole group include combinations of ferrous iron, calcium, and magnesium (Table 56.1).
Chrysotile forms 90% of commercial asbestos and is the least likely to cause tumors and lung fibrosis, because of the relative instability of the fibers in tissues. In North America, most of the amphibole is amosite, whereas in the United Kingdom and Australia, there has been more exposure to crocidolite.
Ferruginous and Asbestos Bodies
When asbestos fibers are inhaled, the alveolar macrophages frequently cover them with an iron-protein-mucopolysaccharide coating, forming “asbestos bodies.” “Ferruginous bodies” also include nonasbestos-based bodies (“pseudoasbestos bodies”) that have a somewhat different histologic appearance and that are not fibrogenic.1,2 Currently, the term “ferruginous body” is used preferentially for nonasbestos-containing fibers.2
Histochemical stains for iron highlight the ferruginous material along asbestos bodies as well as ferruginous material in nonasbestoscontaining ferruginous bodies (Fig. 56.1).
Many asbestos fibers are inhaled and remain uncoated and are not easily visible on routine microscopy. The typical ratio of fibers to bodies is 10-40:1.
In order to prove asbestos origin, the uncoated fiber or core of the asbestos body is analyzed by energy-dispersing x-ray analysis or micro-Raman spectroscopy.1
In tissues, asbestos bodies are golden-brown, beaded, or dumbbell shaped with a thin, translucent core (Figs. 56.2 and 56.3). They are typically found embedded within fibrous tissue, but they may occur in alveolar spaces or within the alveolar macrophages near or around bronchioles, often in areas of anthracosis.2 Pseudoasbestos bodies may have a black core or broad, yellow sheet-like cores and should be distinguished from true asbestos bodies.2
TABLE 56.1 Types of Asbestosis | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
Quantification may be accomplished by routine light microscopy (generally per square centimeter of tissue) or by digestion in sodium hypochlorite and filtering. Scanning electron microscopy and especially transmission electron microcopy are the most sensitive techniques for identifying small, uncoated fibers3 (Fig. 56.4).
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
