Silicosis
Epidemiology and Etiology:
- Inhalation of particles of crystalline silica
- Occupational exposures:
- Sandblasting (banned in most places)
- Abrasive powder manufacture
- Boiler scaling
- Farming (soil in extreme eastern and wester
portions of the US is rich in alpha quartz, the most common form of
crystalline silica)
- Firebrick manufacture
- Foundry work
- Mining (coal, copper, gold, graphite, lead,
mica, and tin)
- Molding and grinding
- Pottery and ceramic manufacture
- Quarry work
- Stonemasonry
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Common sites:
- Upper lung zones tendency
- Thoracic lymph nodes
- Extrathoracic (advanced pulmonary silicosis)
- Liver
- Spleen
- Bone marrow
- Abdominal lymph nodes
Gross features:
- Circumscribed areas of nodular fibrosis
- Firm
- Slate gray
- Nodules a few mm to 1cm in diameter, may become
confluent
- Conglomerate silicosis is defined by areas of
confluent fibrosis > 2 cm
- Cavitation may occur within areas of confluent
fibrosis
- Suggests the possibility of concomitant TB
Histologic features:
- Silicotic nodules (hallmark)
- Subpleural concentration often
- Sharply circumscribed
- Densely collagenous (trichrome)
- Whorled hyalinized collagen
- More loosely arranged concentric whorls of collagen
bundles at the periphery typically
- Macrophages forming a mantle around the
fibrotic centre (recently formed lesions)
- Calcified or ossified (longstanding lesions)
- Faintly birefringent particulates within the
fibrotic nodules
- Larger, brightly birefringent particles maybe
(should not predominate as in silicatosis)
- Absence of multinucleated giant cells generally
(DDx sarcoidosis, infection)
- Giant cells in sarcoidosis may contain fine
needle-like or large, platy birefringent particles (endogenous calcium
carbonate or oxalate, respectively)
- Absence of necrosis (DDx infection)
- Pleural fibrosis, extensive often
- Intra-alveolar granular eosinophilic material
(extremely high exposures to very fine silica particles)
- Appearance closely resembling pulmonary
alveolar proteinosis
- Cholesterol clefts within intra-alveolar
material maybe
- PASD strongly positive typically
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Immunophenotype:
Marker:
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Sensitivity:
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Specificity:
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Molecular features:
- Asymptomatic to markedly dyspneic (conglomerate
silicosis) with hypoxemia to fatal cor pulmonale
Other features:
- Increased risk for acquiring TB
- Low diagnostic yield on transbronchial biopsy
References:
- Leslie KO, Wick MR. Practical Pulmonary Pathology: A
Diagnostic Approach, 2nd ed. (2011)