Lung
Pneumoconiosis
Silicosis
Author: Elliot Weisenberg, M.D.
Last author update: 1 September 2011
Last staff update: 5 January 2021
Copyright: 2003-2025, PathologyOutlines.com, Inc.
PubMed search: silicosis [title] pulmonary
Table of Contents
Definition / general | Gross description | Microscopic (histologic) description | Microscopic (histologic) imagesCite this page: Weisenberg E. Silicosis. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/lungnontumorsilicosis.html. Accessed March 31st, 2025.
Definition / general
- 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
- 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
- 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
Microscopic (histologic) description
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
Microscopic (histologic) images
Images hosted on other servers:
Silicotic nodule
Silica crystals (polarized light)
