Silicosis, Complex



Silicosis, Complex


Kimberly E. Sanchez, MD

Aqeel A. Chowdhry, MD

Tan-Lucien H. Mohammed, MD, FCCP





Key Facts


Terminology



  • Complicated pneumoconiosis: Aggregation of nodules into large masses > 1 cm in diameter, evolves from simple pneumoconiosis


Imaging Findings



  • Progressive massive fibrosis



    • Usually bilateral in upper lobes and superior segments of lower lobes


    • Typically more common in dorsal aspect of lung


    • Right hemithorax earlier and PMF larger than left hemithorax


    • PMF > 4 cm nearly all contain areas of low attenuation due to central necrosis


    • If necrosis or cavitation is seen, mycobacterial infection should be considered


    • As PMF progresses, micronodules decrease in profusion


    • Initially develop in lung periphery and with time migrate towards hilum


  • PET can be markedly positive in PMF, likely due to inflammatory cell activity


Top Differential Diagnoses



  • Talcosis


  • Tuberculosis (TB)


  • Sarcoidosis


Pathology



  • Risk of lung disease related to both dose (intensity) and time (length) of exposure


Diagnostic Checklist



  • Rapid change in radiographic findings concerning for tuberculosis or carcinoma







Axial NECT shows large masses from progressive massive fibrosis image located in the upper lobes and dorsal aspect of the lung.






Coronal NECT shows volume loss and progressive massive fibrosis image, predominantly in the upper lobes.


TERMINOLOGY


Abbreviations and Synonyms



  • Complicated pneumoconiosis, progressive massive fibrosis (PMF), anthracosilicosis


Definitions



  • Lung disease due to inhalation of inorganic mineral dusts containing crystalline silicone dioxide (cement construction products, roof tiles, etc.)


  • Complicated pneumoconiosis: Aggregation of nodules into large masses > 1 cm in diameter, evolves from simple pneumoconiosis



    • Advanced coalescence is known as progressive massive fibrosis


IMAGING FINDINGS


General Features



  • Best diagnostic clue: Micronodular interstitial thickening in upper lung zones with posterior (dorsal) predominance


  • Patient position/location



    • Rounded dusts predominately affect upper lung zones


    • Coal dust accumulates around respiratory bronchioles (coal dust macule)


    • Silica accumulates along lymphatics in centriacinar lobule and lobule periphery


  • Size



    • Micronodules < 10 mm in diameter


    • PMF aggregation > 1 cm


CT Findings



  • More sensitive in detection of nodules and confluence of small opacities


  • Micronodules



    • < 10 mm in centrilobular and subpleural distribution, follow lymphatic pathways


    • Distribution: More profuse in dorsal aspect of upper lobes, right side > left side


    • Nodules may calcify


  • Lymph nodes



    • Typically hilar and mediastinal lymph nodes enlarged


    • May calcify (“eggshell” classic pattern), though may be diffuse or punctate



    • Hilar adenopathy may develop before parenchymal disease


  • Progressive massive fibrosis

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Sep 20, 2016 | Posted by in RESPIRATORY IMAGING | Comments Off on Silicosis, Complex

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