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Lung-nontumor

Pneumoconiosis

Silicosis

Reviewers: Elliot Weisenberg, M.D. (see Reviewers page)
Revised: 26 September 2011, last major update September 2011
Copyright: (c) 2003-2011, PathologyOutlines.com, Inc.

Definition
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● Silica: crystalline silicon dioxide
● Most prevalent chronic occupational disease in the world, due to foundry work, sandblasting, stone cutting and coal mining
● Decades of exposure usually required for symptoms
● Causes a progressive, nodular fibrosing pneumoconiosis
● Acute silicosis: less common, due to heavy exposure; similar to alveolar proteinosis with generalized accumulation of lipoproteinaceous material within alveoli
● Crystalline forms of silica are more fibrogenic than amorphous forms; quartz is particularly fibrogenic, although quartz plus other minerals are less fibrogenic
● Quartz causes directly injury to membranes via SiOH groups and by free radicals generated by crushing silica
● Silica also causes macrophages to release mediators which stimulate fibroblasts, including tumor necrosis factor
● Initial lesions are in upper lung zones, more fibrotic than coal workers’ pneumoconiosis
● Talc, vermiculite and mica are noncrystalline silicates that less commonly cause pneumoconiosis
● Detect on routine chest Xray as a fine nodularity in upper lobes, but normal pulmonary function
● No symptoms until progressive massive fibrosis, then disease progresses with impaired pulmonary function
● Disease may progress even after exposure to silica ceases
● Not associated with lung cancer

Gross description
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● Early, tiny, discrete pale to black (if coal dust present) nodules in upper zones of lungs, progressing to hard collagenous scars
● Nodules have stellate shape at the edges, may cavitate due to tuberculosis or ischemia
● Fibrosis present in hilar nodes and pleura
● May see eggshell calcification in nodes on Xray

Micro description
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Early lesions:
● Small nodules of fibroblasts and histiocytes with abundant silica, that become less cellular and more hyalinized with time
● With progressive massive fibrosis, see hyalinized and condensed collagen, needle-like spicules with pointed ends, 5 microns or less, birefringent with polarization and intra- or extracellular

Micro images
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Silicotic nodule


Silica crystals (polarized light)

Virtual slides
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Silicosis

End of Lung-nontumor > Pneumoconiosis > Silicosis

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