Mesothelioma

Key Features

Essentials of Diagnosis

• Unilateral, nonpleuritic chest pain and dyspnea

• Pleural effusion or pleural thickening or both on chest radiographs

• Mesothelial cells in pleural fluid or tissue

• Commonly, a distant (> 20 years earlier) history of exposure to asbestos

General Considerations

• Primary tumors arising from the mesothelial surfaces of the pleura (80% of cases) or peritoneum (20% of cases)

• Mesothelioma is almost always malignant (especially, pleural location), with malignant cells on histology; rarely, mesothelioma is benign (usually, abdominal location) with cystic, adenomatoid, fibrous changes on histology

• 75% of pleural mesotheliomas are diffuse (usually malignant)

• The average interval between onset of symptoms and diagnosis is 2–3 months, with median age at diagnosis of 72 to 74 years in Western countries

• The latent period between asbestos exposure and onset of symptoms ranges from 20 to 40 years

Demographics

• Men outnumber women 3:1

• Malignant pleural mesothelioma is associated with asbestos exposure (60–80% of cases); the lifetime risk to asbestos workers is 10%

• Cigarette smoking significantly increases the risk of bronchogenic carcinoma in asbestos workers and aggravates asbestosis, but there is no association between smoking and mesothelioma independent of the asbestos exposure

• Asbestos exposure occurs from work in

  • Mining

  • Milling

  • Manufacturing

  • Shipyard work

  • Insulation

  • Brake linings

  • Building construction and demolition

  • Roofing materials

  • Other asbestos-containing products (eg, some "popcorn" ceilings)

Clinical Findings

Symptoms and Signs

• Insidious onset of shortness of breath, nonpleuritic chest pain, and weight loss

• Physical findings include

  • Dullness to percussion

  • Diminished breath sounds

  • Clubbing of fingers (some cases)

• Malignant pleural mesothelioma progresses rapidly as the tumor spreads along the pleural surface to involve the pericardium, mediastinum, and contralateral pleura

• Tumor may eventually extend beyond the thorax to involve abdominal lymph nodes and organs

Differential Diagnosis

• Chronic organized empyema

• Sarcoma

• Metastatic cancer to the pleura, especially adenocarcinoma

• Malignant fibrosing histiocytoma

• Other causes of pleural effusion (see Pleural Effusion)

Diagnosis

Laboratory Tests

• Pleural fluid analysis often reveals a hemorrhagic exudate

• Cytologic tests of pleural fluid are often negative

• Soluble mesothelin-related peptide and fibulin-3 may be found in serum or pleural fluid (or both) of patients with malignant mesothelioma

Imaging Studies

• Radiographic findings

  • Nodular, irregular, unilateral pleural thickening

  • Varying degrees of unilateral pleural effusion

• CT helps determine the extent of pleural involvement

• PET-CT helps differentiate benign from malignant pleural disease, improve staging accuracy, and identify candidates for aggressive surgical approaches

Diagnostic Procedures

• Thoracentesis

• Video-assisted thoracoscopic surgery (VATS) biopsy is usually necessary to obtain an adequate specimen for histologic diagnosis; special stains and electron microscopy ...