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Silicosis and Coal Worker Pneumoconiosis: Imaging
Updated: Jun 23, 2009
Radiography
Reticular and small nodular opacities are present in the middle and upper lung zones. Also present are large, round opacities predominantly on the right; these are consistent with conglomerate nodules. Eggshell calcification of the mediastinal lymph nodes is also apparent, most notably in the regions of the right paratracheal and aortopulmonary window.
Silicosis with progressive massive fibrosis. Image shows large, conglomerate nodules in both the middle and upper lung zones. Peripheral hyperlucency represents emphysematous lung tissue secondary to central migration of the large nodules. Also shown is evidence of volume loss in both upper lobes.
Simple silicosis is depicted as widespread nodules measuring 2-5 mm in diameter, with a predominance in the middle and upper lung zones.
Images show small nodules predominantly in the middle-to-upper lung zones, several of which are calcified. The large, round opacity overlying the posterior aspect of the fifth rib and the anterior aspect of the second rib on the right side is consistent with a conglomerate nodule.
Image shows small nodules predominantly in the middle-to-upper lung zones, several of which are calcified. Eggshell calcification is present in the bilateral hilar lymph nodes. The large mass in the infrahilar region of the right lung is consistent with progressive massive fibrosis.
Findings
On chest radiographs and CT scans, the appearances of silicosis and CWP are almost identical. However, the nodules seem to be small on chest radiographs.
Approximately 20 years of exposure is required to result in a positive chest radiograph. Chest radiography is approximately 80% sensitive, and the usual findings are multiple, small (<1 cm) lung opacities. These opacities tend to occur in the upper and posterior regions of the lungs. They are usually round and well circumscribed. Their size and opacity vary little. These nodules are calcified in 10-20% of patients. With the progression of the disease, the nodules can merge to form large opacities. This change is indicative of PMF, and it occurs more frequently in silicosis than in CWP.
The lesions must be at least 1 cm to be classified as PMF. Enlarged, calcified (eggshell calcification) lymph nodes are usually in the hila and mediastinum. PMF has a distinct appearance on chest radiography. PMF is usually symmetrical, but it may be unilateral. It appears as irregular, masslike or sausage-shaped opacities that are typically seen in the posterior upper lobes with associated hilar retraction.11 These lesions are usually lenticular instead of round and therefore appear less dense than expected on frontal images.
PMF has an angel's-wing appearance on chest radiographs. They are large lesions kept apart from the pleura by aerated lung. Sequential imaging shows that these lesions tend to migrate toward the hila, leaving behind peripheral areas of emphysema. The emphysema and lung volume loss help distinguish unilateral PMF from lung cancer. Cavitation may be a complication, with ischemic necrosis or concomitant tuberculous infection. Punctate, linear, or massive calcifications of the PMF lesions may be noted.21
Computed Tomography
High-resolution CT images of advanced coal-worker's pneumoconiosis with parenchymal nodules, calcifications, and progressive and massive fibrosis. Advanced-stage silicosis is indistinguishable from this condition.
High-resolution CT images of advanced coal-worker's pneumoconiosis with parenchymal nodules, calcifications, and progressive and massive fibrosis. Advanced-stage silicosis is indistinguishable from this condition.
Findings
CT findings
On CT scans, these diseases appear as small, discrete nodules that have a predilection for the posterior portions of the upper lobes. The size of the nodules should be well correlated on CT scans and on chest radiographs.
On CT, PMF typically appears as irregular, lens-shaped, bilateral, large (>10 mm) attenuations in the posterior portions of the upper lobes. These lesions are often well circumscribed, calcified, and surrounded by cicatricial emphysema. Thickening of the adjacent extrapleural fat is common. Masses larger than 4 cm in diameter may exhibit central necrosis. Cavitation is infrequent. If necrosis or cavitation is seen in PMF, mycobacterial infection should always be considered. Pulmonary massive fibrosis can be misdiagnosed as bronchogenic carcinoma when pathognomonic characteristics, such as bilateral lens-shaped attenuations, well-defined borders, irregular calcifications, and lung nodularity, are missing.
HRCT findings
The typical appearance of pneumoconiosis on HRCT is branching and nonbranching centrilobular nodules that represent bronchiolar lesions. These lesions can be divided into 2 patterns: (1) ill-defined, fine, branching lines or nodules and (2) well-defined, discrete nodules. If present, interstitial fibrosis manifests as traction bronchiectasis, honeycombing, or large attenuations.21
On HRCT, lesions classified as p in the ILO criteria appear as small, branching structures or a group of small dots. They are usually associated with centrilobular emphysema. Lesions designated as q or r appear as either discrete, well-circumscribed, round nodules or as irregularly shaped, contracted nodules. Fusion of the small nodules can produce a large confluent lesion.11
On HRCT, silicoproteinosis appears as a ground-glass or alveolar pattern; no nodules are observed.
CWP appears as focal emphysema and nodularity of the posterior portions of the upper lobes. Nodules smaller than 7 mm are micronodules, those 7-20 mm are macronodules, and those larger than 20 mm are PMF. According to the ILO criteria, round nodules smaller than 1.5 mm are p, those 1.3-3 mm are q, and those 3-10 mm are r. Lesions of CWP also become cavitated and calcified.
On HRCT, CWP with p lesion appears as little, branching lines or ill-defined, punctate attenuations. In some cases, small areas of low attenuation with a central dot can be seen. These areas are thought to represent either irregular fibrosis surrounding respiratory bronchioles or dust macules on dilated respiratory bronchioles. Lesions classified as q and r types are well-circumscribed, round, or contracted nodules.21
Subpleural micronodules can be seen on HRCT. These lesions can coalescence into large pseudoplaques in CWP.
The appearance of PMF is similar to that of silicosis.
More on Silicosis and Coal Worker Pneumoconiosis |
| Overview: Silicosis and Coal Worker Pneumoconiosis |
 Imaging: Silicosis and Coal Worker Pneumoconiosis |
| Follow-up: Silicosis and Coal Worker Pneumoconiosis |
| Multimedia: Silicosis and Coal Worker Pneumoconiosis |
| References |
| Further Reading |
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References
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Further Reading
Clinical guidelines
Guidelines for the prevention, identification and management of occupational asthma: evidence review and recommendations.
British Occupational Health Research Foundation - Private Nonprofit Organization. 2004. 88 pages. NGC:003853
Mycobacterial infections.
New York State Department of Health - State/Local Government Agency [U.S.]. 2005 May (revised 2006 Sep). 20 pages. NGC:006468
Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease.
Global Initiative for Chronic Obstructive Lung Disease - Disease Specific Society
National Heart, Lung, and Blood Institute (U.S.) - Federal Government Agency [U.S.]
World Health Organization - International Agency. 2006 (revised 2007). 109 pages.
Clinical trials
Specialized Center of Research in Occupational and Immunologic Lung Disease
Related eMedicine topics
Asbestosis
Histoplasmosis (Thoracic)
Asbestosis (Pulmonology)
Coal Worker's Pneumoconiosis (Pulmonology)
Pulmonary Fibrosis, Interstitial (Pulmonology)
Silicosis (Pulmonology)
Keywords
silicosis, pneumoconiosis, diffuse parenchymal lung disease, CWP, black lung, coal miner's lung, coalminer's lung, coal-miner's lung, coalminer lung, miner's asthma, coal miner's asthma, coalminer's asthma, coalminer asthma, pneumokoniosis, diffuse interstitial fibrosis, DIF, anthracosilicosis, anthracotic tuberculosis, anthracosis, simple coal worker's pneumoconiosis, SCWP, complicated coal worker's pneumoconiosis, CCWP, pulmonary massive fibrosis, PMF, coal macules, emphysema, Caplan syndrome, Caplan's syndrome, Caplan nodules, Caplan's nodules, Caplan lesions, Caplan's lesions, intrapulmonary nodules, silica, silicon dioxide, SiO2, crystalline silica, pneumoconioses, acute silicoproteinosis, accelerated silicosis, simple chronic nodular silicosis, complex chronic nodular silicosis, dust exposure
