Lung - nontumor
Pneumoconiosis
Silicosis

Author: Elliot Weisenberg, M.D. (see Authors page)

Revised: 2 March 2017, last major update September 2011

Copyright: (c) 2003-2017, PathologyOutlines.com, Inc.

PubMed search: silicosis [title] pulmonary

Cite this page: Silicosis. PathologyOutlines.com website. http://pathologyoutlines.com/topic/lungnontumorsilicosis.html. Accessed October 20th, 2017.
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)