Pleural Plaques
Eric J. Stern, MD
DIFFERENTIAL DIAGNOSIS
Common
Asbestos-related Pleural Disease
Prior Empyema
Prior Hemothorax or Other Injury to Pleura
Pleural Effusion
Extrapleural Fat
Less Common
Pleural Metastases
Primary Pleural Tumor
Malignant Mesothelioma
Pleurodesis
Rare but Important
Postcardiac Injury Syndromes
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
Radiographs
Look for any associated abnormalities
Underlying lung disease: Lung cancer, metastases
Overlying chest wall disease or injury
Rib fractures
Detection of calcification is useful distinguishing feature
Asbestos-related plaque
Talc pleurodesis
Treated empyema or pleural tuberculosis
Distribution of “pleural thickening” helpful in determining etiology
Symmetric: Consider asbestos-related
Asymmetric: Less likely asbestos-related
In patients with asbestos exposure, must distinguish plaques from extrapleural fat
CT
Most useful examination for distinguishing fat from fluid from solid thickening
Distinguishes true pleural disease from pleural-based lung abnormalities or chest wall disease
Look for any associated abnormalities
Underlying lung scarring, inflammation, or masses
Overlying rib fractures or callous around healed fractures, metastases, prior surgery
Helpful Clues for Common Diagnoses
Asbestos-related Pleural Disease
Distribution
Hemidiaphragms
Paravertebral
Antero-/lateral
Bilateral and fairly symmetric
Parietal pleura, only rarely involves visceral pleura
Spares apices and costophrenic sulci
Well-demarcated elevations of pleura best seen in profile
Often calcified: Radiographic “holly leaf” sign
Large, thick plaques associated with round atelectasis
Biomarker of exposure to asbestos
Benign disease
Rarely extend more than 4 rib interspaces; 2-5 mm thick; relative symmetric involvement
Linear band of calcification when viewed in profile; irregular “holly leaf” configuration en face
Prior Empyema
Adjacent lung abnormal, scarring from previous pneumonia
Usually unilateral
Focal or diffuse pleural scarring
Parietal and visceral involvement
Can be associated with prominent focal extrapleural fat, as a result of chronic pleural inflammation
Prior Hemothorax or Other Injury to Pleura
Unilateral, multiple healed rib fractures
History or evidence of prior thoracotomy (resected rib)
History of prior thoracostomy tube
Pleural Effusion
Small volume mimics thickened pleura
Free-flowing effusions will be mobile
Bilateral decubitus radiographs
Prone and supine CT
Loculated effusions should appear more lenticular
Involves fissures, apices, and costophrenic sulci, unlike asbestos-related pleural disease
Simple transudative effusions are near water attenuation
Exudative effusions have attenuation between water and soft tissue
“Split pleura” sign
Enhanced or thickened pleura separated by lower attenuation fluid suggests empyema
Extrapleural Fat
Fat attenuation on CT
Radiographs, most evident on lateral chest wall convexities
Symmetric, mid-lateral chest wall at level of 4th to 8th ribs; may extend into fissures
Associated with other fat deposition: Pericardial fat pads, widened mediastinum
No calcifications
Helpful Clues for Less Common Diagnoses
Pleural Metastases
Usually known primary tumor, commonly adenocarcinoma
Typically nodular or “lumpy bumpy”
Extend into fissures
Effusions commonly associated
May be indistinguishable from mesothelioma
Malignant Mesothelioma
Very similar or indistinguishable appearance to metastatic adenocarcinoma pleural metastases
Needs histologic differentiation
Almost all have history of asbestos exposure
Unilateral
Involves parietal and visceral pleura, pericardium
Circumferential, nodular thickening
Not usually focal like simple plaques
Markedly reduces volume of involved hemithorax
Often associated with asbestos-related plaques
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