Pleural Mass

Jonathan H. Chung, MD

DIFFERENTIAL DIAGNOSIS

Common

Pleural Pseudotumor
Pleural Plaque
Pleural Thickening
Empyema
Rounded Atelectasis
Subpleural Lung Cancer

Less Common

Pleural Metastasis
Pulmonary Infarctions (Subpleural)
Extrapleural Abnormality
- Benign or Malignant Chest Wall Mass
- Extrapleural Hematoma
- Fracture
Pleurodesis

Rare but Important

Lymphoma
Malignant Mesothelioma
Fibrous Tumor of Pleura

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Pleural vs. subpleural (pulmonary)
- Pleural: Obtuse margins with chest wall, well-defined margins with lung, no air bronchograms
- Subpleural (pulmonary): Acute margins with chest wall, ill-defined margins with lung, air bronchograms
Differentiation of extrapleural vs. pleural abnormality can be difficult
- Extrapleural component present if concomitant effect on extrapleural structures
  - Rib destruction in extrapleural tumor
  - Extension of mass into chest wall on CT
  - Internal displacement of extrapleural fat
Incomplete border sign on radiograph highly suggestive of extrapulmonary (pleural or extrapleural) lesion
- Margins partially sharp and partially unsharp

Helpful Clues for Common Diagnoses

Pleural Pseudotumor
- Loculated pleural fluid in interlobar fissure, usually minor fissure
- History of congestive heart failure
- Oval shape, peripheral tapering along margins of pseudotumor
Pleural Plaque
- Related to previous asbestos exposure
- Bilateral focal regions of pleural thickening, ± calcification, often symmetric
- Posterolateral, diaphragmatic, and pericardial preponderance; sparing of apices and costophrenic angles
Pleural Thickening
- Related to asbestos exposure, previous infection or inflammation, hemothorax
- Usually smooth thickening of pleura, often diffuse, ± foci of calcification
- May affect costophrenic angles; often broad extension as opposed to focality of pleural plaques
Empyema
- Pus in pleural space; most often from pneumonia/pulmonary abscess
- Loculation, split pleura sign
  - Lenticular shape
  - Nondependent location
Rounded Atelectasis
- Definitive diagnosis on CT requires 4 findings
  - Pleural thickening, pleural effusion, or pleural plaque
  - Broad-based intimate attachment of mass-like consolidation to pleural abnormality
  - Volume loss
  - Comet tail (or hurricane) sign: Swirling of bronchovasculature into mass-like consolidation
Subpleural Lung Cancer
- Most common in upper lung zone (2/3 of primary lung cancers)
- Spiculated margins, pleural tail, thick-walled cavitation
- Hilar and mediastinal lymphadenopathy

Helpful Clues for Less Common Diagnoses

Pleural Metastasis
- Adenocarcinoma most common; drop metastases from invasive thymoma
- Unexplained unilateral pleural effusion, irregular pleural thickening, and nodules ± enhancement
Pulmonary Infarctions (Subpleural)
- Most often from pulmonary arterial embolism
- Usually in setting of superimposed cardiac dysfunction (cardiomyopathy, congestive heart failure)
  - Both pulmonary and bronchial arterial supply to lung reduced
- Lower lung predominant, peripheral/subpleural, wedge-shaped consolidation
- Resolves over months (retains its original shape) rather than patchy resolution as in pneumonia
Extrapleural Abnormality
- Mass effect on or destruction of extrapleural structures
- Extrapleural hematoma
  - High association with rib fractures and elderly patients; sequela of blunt or penetrating trauma
  - Localized hyperdense fluid collection often internally displacing extrapleural fat stripe
  - Biconvex shape suggests arterial injury (usually intercostal)
Pleurodesis
- Iatrogenic fusion of visceral and parietal pleura; talc most often used
- Treatment of recurrent pleural effusion (most often malignant etiology)
- Unilateral high density foci, most often dependent
- Associated pleural thickening (which can be nodular) or loculated pleural fluid

Helpful Clues for Rare Diagnoses

Lymphoma
- Concomitant mediastinal lymphadenopathy; ± pleural effusion
- Can be difficult to differentiate pleural from extrapleural involvement
Malignant Mesothelioma
- Stigmata of previous asbestos exposure: Pleural plaques, pleural thickening, pleural effusion
- Lobulated pleural thickening; small hemithorax
- CT findings that suggest malignant pleural disease (mesothelioma or metastases)
  - Circumferential involvement of pleura, including visceral pleura
  - Involvement of mediastinal aspect of pleura
  - Nodularity
  - Thickness greater than 1 cm
Fibrous Tumor of Pleura
- Well-marginated, large pleural mass with avid enhancement (may be heterogeneous in larger tumors)
- Margins with chest wall may be acute in large tumors
- Majority arise from visceral pleura; up to half pedunculated; may be mobile

Image Gallery

Frontal radiograph shows an oval mass

in the peripheral mid right lung in this patient with cardiomegaly and history of heart failure.

Lateral radiograph shows that the mass is located along the minor fissure and has tapered anterior and posterior margins (best seen anteriorly

). These findings are most consistent with a loculated pleural fluid collection.

(Left) Lateral radiograph shows calcified pleural plaques

along the anterior, posterior, and diaphragmatic aspects of the pleura. (Right) Frontal radiograph (magnified) shows the typical “holly leaf” appearance of an en face calcified pleural plaque on the anterior pleural surface.

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