What is the typical appearance of mesothelioma on a computed tomography (CT) scan?

Typical Appearance of Mesothelioma on CT Scan

The typical appearance of mesothelioma on CT scan includes diffuse or nodular pleural thickening, pleural effusion, thickening of interlobar fissures, and in some cases contraction of the involved hemithorax. 1

Key CT Features of Malignant Pleural Mesothelioma (MPM)

Common Primary Findings

• Pleural thickening (seen in 88-94% of cases) - often diffuse or nodular in appearance 1, 2
• Pleural effusion (seen in 74-76% of cases) - frequently unilateral and may be loculated 1, 2, 3
• Thickening of interlobar fissures (seen in 47-86% of cases) - highly suggestive of MPM 3, 4
• Unilateral involvement - bilateral disease is rare, occurring in only about 3% of cases 1

Additional Characteristic Features

• Volume changes in the affected hemithorax - either contraction (27-42% of cases) or enlargement (10% of cases) 2, 4
• Nodular pleural thickening - more specific for malignancy with sensitivity of 37-48% and specificity of 86-97% 1
• Pleural thickening >1 cm - suggestive of malignancy with sensitivity of 35-47% and specificity of 64-94% 1
• Mediastinal pleural involvement - sensitivity of 70-74% and specificity of 83-93% 1

Less Common Features

• Chest wall invasion - may be difficult to detect on CT alone 1, 2
• Diaphragmatic invasion - better visualized with MRI than CT 1
• Interlobar fissure nodularity - highly specific (100%) but low sensitivity (10%) 1
• Concurrent pleural calcifications or plaques - indicative of previous asbestos exposure, seen in approximately 16-20% of cases 2, 4
• Spontaneous pneumothorax - a rare presentation of MPM 5

Differentiating MPM from Metastatic Pleural Disease

Features Favoring MPM

• Pleural thickening - more common and typically more extensive in MPM 3
• Loculated pleural effusion - seen in 58.8% of MPM cases 3
• Thickening of interlobar fissures - more characteristic of MPM 3, 6
• Presence of pleural plaques - suggests asbestos exposure history 1

Features Favoring Metastatic Disease

• Free-flowing pleural effusion - seen in 71.7% of metastatic cases 3
• Parenchymal lung infiltration - more common in metastatic disease (65.8%) 3
• Lung parenchymal involvement - nodules or masses within the lung tissue 1
• Mediastinal or hilar lymph node enlargement - more suggestive of metastatic pleural disease 1

Technical Considerations for Optimal CT Imaging

• Intravenous contrast enhancement - improves visualization of pleural tumors 1
• Multi-planar reconstruction - axial, coronal, and sagittal planes using 1-2 mm slice thickness 1
• Extended field of view - should include the entire chest wall and pleural spaces, extending caudally to at least L3 vertebral level to ensure coverage of the posterior costophrenic angles 1
• Soft-tissue kernel reconstruction - allows optimal assessment of pleural space and adjacent tissues 1

Limitations of CT in MPM Diagnosis

• CT alone is unsuitable for definitive diagnosis of MPM, though findings can be highly suggestive 1
• CT may underestimate chest wall and mediastinal invasion in some patients 2
• Thoracoscopy with biopsy remains the recommended method for definitive diagnosis 1
• CT has limited accuracy for staging MPM using current staging systems 1

Diagnostic Accuracy of CT vs Other Modalities

• Overall diagnostic accuracy of CT for pleural malignancy: 68-97% sensitivity, 78-89% specificity 1
• MRI is superior to CT for detecting invasion through diaphragm and chest wall 1
• PET-CT has higher accuracy for staging MPM across T, N, and M criteria compared to CT alone 1
• Ultrasound can be complementary, particularly for guiding biopsy of pleural lesions 1