TYPES OF PLEURAL MASSES
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Mesothelioma
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Solitary Fibrous Tumor of the Pleura
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Other Rarer Pleural Masses ( Table 48-1 )
TABLE 48-1 ▪
Classification of Pleural Masses
Benign
Malignant
Solitary fibrous tumor of the pleura
Mesothelioma
Pleural lipoma
Angiosarcoma
Angiomas
Synovial sarcoma of the pleura
Fibroma
Primary pleural lymphoma
Neurofibroma
Ectopic pleural thymoma
Calcifying fibrous pseudotumor of the pleura
Metastasis
From Butchart EG, Ashcroft T, Barnsley WC, et al. Pleuropneumonectomy in the management of diffuse malignant mesothelioma of the pleura. Thorax 1976;31:15-24.
MALIGNANT PLEURAL MESOTHELIOMA
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Epidemiology
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Rare and very aggressive, primary malignant pleural tumor
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Originates from the mesothelial cells that line the parietal and visceral pleura
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Usually diagnosed in the fifth to seventh decades of life
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Strong male predominance (80%)
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2500 cases per year in the United States
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2000 cases in men
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500 cases in women
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Incidence: 15 cases per million population
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Incidence rising in the United States, particularly in men aged 75 years or older
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Incidence rising in Europe, with 5000 dying in 1998 and 9000 projected to die by 2018
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Occupational exposure to asbestos is the main risk factor
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Association between lung cancer and asbestos exposure first established in 1955
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80% patients with mesothelioma have asbestos exposure
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Only 10% of those with asbestos exposure develop mesothelioma
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Latency period between exposure and death is generally between 25 to 49 years
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Human simian virus (SV)-40 may play a role because human mesothelial cells are highly susceptible to infection by the virus. SV-40 may have contaminated vaccines in the 1960s.
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Smoking and asbestos have synergistic effect in lung cancer development, but there is no known association of smoking and mesothelioma development.
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Clinical features
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Symptoms
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Dyspnea and nonpleuritic chest wall pain (60%) are most common.
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Patients can be asymptomatic.
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Typically, progressive shortness of breath, chest pain, anorexia and weight loss as disease advances.
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Signs
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Ipsilateral dullness to percussion, decreased breath sounds on affected side, decreased chest wall excursion at base of hemithorax, physical distortion of the ribcage with diseased side smaller than the contralateral hemithorax.
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Ninety percent have unilateral pleural effusion.
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Clubbing occurs in less than 1%.
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Advanced disease almost always due to local invasion of chest wall, pericardium, or diaphragm. Distal metastases are rare.
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Invasion of contralateral lung or peritoneal cavity occurs in 10% to 20% cases.
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Local invasion can rarely lead to dysphagia, Horner’s syndrome, superior vena cava syndrome, spinal cord compression, cardiac tamponade, vocal cord paralysis, or diaphragm paralysis.
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Prognosis
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Median survival from the onset of symptoms without therapy is generally 6 months; with single-modality therapy, survival can be increased to 9 to 12 months.
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Death is usually secondary to respiratory failure, cachexia, or infection.
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Poor prognostic factors
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LDH level greater than 500
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Poor performance status
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Chest pain
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Platelet count greater than 400,000
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Nonepithelial histology
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Age older than 75 years
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Male gender
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Pathophysiology
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Asbestos fibers
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Serpentine asbestos fibers are large, curly, and not able to travel to distal airways.
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Amphibole asbestos fibers are narrow and straight and travel to distal pulmonary airways and are clearly associated with mesothelioma formation.
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Asbestos miners
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Shipyard workers
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Naval veterans serving on World War II era ships
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Insulation in cold environments
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Family members of workers with heavy exposure (from clothing)
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Pathology—three types
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Epithelial
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Fifty percent of cases
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More favorable prognosis
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Sarcomatoid
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Fifteen percent of cases
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More aggressive course, worse prognosis
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Mixed
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Thirty-five percent of cases
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Because sarcomatoid element is aggressive, similar prognosis to pure sarcomatoid variant
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Vimentin negative
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Cytokeratin positive
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Diagnosis
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Chest x-ray study (CXR) typically shows unilateral pleural thickening, pleural mass, pleural effusion, and basilar atelectasis ( Fig. 48-1 ). Plaques are signs of asbestos exposure but may not be a precursor to mesothelioma
Figure 48-1
A, Chest radiograph (posteroanterior and lateral) showing unilateral left pleural based masses. B, Chest radiograph in another patient showing advanced mesothelioma. Still evident are large pleura-based masses on the left, together with extensive opacification due to tumor encasement. This patient had significant chest wall pain and dyspnea, and the latter was due to thoracic restriction by the tumor.
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Computed tomography (CT) scan of the chest
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Unilateral pleural effusion (74%)
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Thickened irregular pleural based masses (92%)
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Chest wall invasion (18%)
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Pleural plaques (20%)
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Differential diagnosis includes
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Fibrothorax
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Rheumatologic causes
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Adenocarcinoma
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Magnetic resonance imaging (MRI) helpful in determining extent of local invasion into mediastinum, chest wall, or diaphragm
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Echocardiography used to assess pericardial involvement, pulmonary hypertension, and baseline ejection fraction
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Positron emission tomography (PET) scan can help rule out extrathoracic disease that would preclude surgical intervention. Mesothelioma is frequently not intense in tracer uptake.
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Serum markers may be helpful in near future.
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Serum mesothelin–related protein is elevated in 84% of patients with malignant mesothelioma and is elevated in less than 2% of patients with other pleural diseases.
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Serum mesothelin–related protein levels increase with mesothelioma progression and decrease with tumor resection, making it perhaps useful in monitoring disease recurrence.
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Thoracentesis is frequent initial diagnositic step for unilateral pleural effusion.
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Unreliable because fluid cytology can be negative (pleural biopsy preferred). Also, very difficult to distinguish mesothelioma from sarcomas and adenocarcinomas based on fluid cytology alone.
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CT-guided pleural biopsy
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Sixty percent yield (single attempt) to 85% yield (multiple attempts)
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Thorascopy-guided pleural biopsy (best workup)
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Greater than 90% yield
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Rare complications include bleeding, infection, air leak
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Forty percent chance of seeding tumor at the port sites
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Port should be placed in line of posterolateral thoracotomy incision. If patient seeks multimodality therapy (i.e., chemotherapy, radiation, and surgery), this location will facilitate wide local excision of the port site during surgical therapy.
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Open thoracotomy and pleural biopsy is discouraged.
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Staging
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Butchardt: earliest system, now rarely used ( Table 48-2 )
TABLE 48-2 ▪
Butchart Staging System
Stage
Description
I
Tumor confined within the pleural envelope
II
Invading chest wall or mediastinal structures
III
Invading through the diaphragm or into contralateral pleura
IV
Distant metastases
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Brigham and Women’s system ( Table 48-3 )
TABLE 48-3 ▪
Revised Staging System for Malignant Pleural Mesothelioma
Stage
Description
I
Disease completely resected within the capsule of the parietal pleura without adenopathy: ipsilateral pleura, lung, pericardium, diaphragm, or chest wall limited to previous biopsy sites
II
All of stage I with positive margins and/or intrapleural adenopathy
III
Local extension of disease into the chest wall or mediastinum; heart, or through diaphragm, peritoneum or with extrapleural lymph node involvement
IV
Distant metastatic disease
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TNM staging, International Mesothelioma Interest Group ( Table 48-4 )
TABLE 48-4 ▪
TNM Staging System and TNM Stage Grouping
Stage
Description
The TNM Staging System
T1
Tumor involves ipsilateral parietal pleura, with (T1b) or without (T1a) focal involvement of visceral pleura
T2
Confluent visceral pleural tumor, invasion of diaphragm muscle, and/or invasion of lung parenchyma
T3
Invasion into endothoracic fascia or mediastinal fat, a single focus invading chest wall, soft tissue and/or nontransmural involvement of the pericardium
T4
Diffuse/multifocal chest wall soft tissue invasion, rib involvement, transdiaphragmatic invasion, invasion of mediastinal organs, direct extension to contralateral pleura, invasion of spine, extension through pericardium, malignant pericardial effusion, invasion of myocardium or brachial plexus.
N0
No regional lymph node metastases.
N1
Metastases in ipsilateral bronchopulmonary or hilar lymph node.
N2
Metastases in subcarinal and/or ipsilateral internal mammary or mediastinal lymph nodes
N3
Metastases in contralateral mediastinal, internal mammary or hilar lymph nodes, and/or ipsilateral or contralateral supraclavicular or scalene lymph nodes
M0
No distant blood-borne metastases
M1
1 or more distant blood-borne metastases
TNM Stage Grouping
I
T1
N0
M0
II
T2
N0
M0
III
T1, T2
N1
M0
T1, T2
N2
M0
T3
N0-2
M0
IV
T4
N0-3
M0
T1-4
N3
M0
T1-4
N0-3
M1
From International Mesothelioma Interest Group. A proposed new international TNM staging system for malignant pleural mesothelioma. Chest 1995;108:1122-1128.
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Treatment
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The key is to use a multimodality approach.
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Single modality (i.e., surgery alone, chemotherapy alone, radiation alone) palliates symptoms but does not significantly affect survival.
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Surgery
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Thoracoscopy and pleurodesis for diagnosis and palliation
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Pleurectomy
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Removal of visceral and parietal pleura of entire ipsilateral lung
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May include removal of ipsilateral pericardium and diaphragm.
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Extrapleural pneumonectomy (EPP) ( Fig. 48-2 )
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Most aggressive
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En bloc resection of lung, pericardium, ipsilateral diaphragm, and visceral and parietal pleura, with reconstruction of the diaphragm and pericardium
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Major operation associated with high morbidity and mortality rates. Appropriate for young patients with low comorbidity and preserved functional status.
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Consider referral to major center with extensive experience.
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