Malignant Mesothelioma
- Most common primary neoplasm of pleura
- Prevalence
- 2,000-3,000 cases/year in US
- Etiology
- Asbestos exposure
- Zeolite (nonasbestos
mineral fiber)
- Chronic inflammation (TB, empyema)
- Radiation
- Peak age
- Histology
- Epithelioid (60%)
- Sarcomatoid (15%)
- Biphasic (25%)
- Intracellular asbestos fibers in 25%
- Carcinogenic potential: crocidolite >
amosite > chrysotile >
actinolite,
anthophyllite, tremolite
- Occupational exposure of asbestos found
in only 40-80% of all cases
- 5-10% of asbestos workers will develop
mesothelioma (risk factor of 30X compared with general
population)
- No relation to duration/degree of
exposure to asbestos or smoking history
- Latency period
- 20-45 years
- Earlier than asbestosis
- Later than asbestos-related lung
cancer
- Pathology
- Multiple tumor masses involving
predominantly the parietal pleura and to a lesser degree the
visceral pleura
- Progresses to thick
sheetlike / confluent masses
resulting in lung encasement
- Associated with
- Peritoneal mesothelioma
- Hypertrophic osteoarthropathy (10%)
- Staging (Boutin
modification of Butchart staging)
- IA confined to ipsilateral parietal /
diaphragmatic pleura
- IB+ visceral pleura, lung ,
pericardium
- II invasion of chest wall /
mediastinum (esophagus, heart, contralateral pleura) or
metastases to thoracic lymph nodes
- III penetration of diaphragm with
peritoneal involvement or metastases to
extrathoracic lymph nodes
- IV distant hematogenous metastases
- Stage at presentation
- II in 50%
- III in 28%
- I in 18%
- IV in 4%
- Clinical signs and symptoms
- Nonpleuritic
(56%) / pleuritic chest pain (6%)
- Dyspnea (53%)
- Fever + chills + sweats (30%)
- Weakness, fatigue, malaise (30%)
- Cough (24%)
- Weight loss (22%)
- Anorexia (10%)
- Expectoration of asbestos bodies (=
fusiform segmented rodlike
structures = iron-protein deposition on asbestos fibers)
- Spread
- Contiguous: chest wall, mediastinum,
contralateral chest, pericardium, diaphragm, peritoneal
cavity; lymphatics, blood
- Lymphatic
- Hilar + mediastinal (40%)
- Celiac (8%)
- Axillary + supraclavicular (1%)
- Cervical nodes
- Hematogenous: lung, liver, kidney,
adrenal gland
- Imaging findings
- Extensive irregular lobulated bulky
pleural-based masses typically >5 cm / pleural thickening
(60%)
- Exudative / hemorrhagic unilateral
pleural effusion (30-60-80%) without mediastinal shift;
effusion contains hyaluronic acid in 80-100%; bilateral
effusions (in 10%)
- Distinct pleural mass without effusion
(<25%)
- Associated with pleural plaques in 50%
= pathologic HALLMARK of asbestos exposure
- Pleural calcifications (20%)
- Circumferential encasement =
involvement of all pleural surfaces (mediastinum,
pericardium, fissures) as late manifestation
- Extension into interlobar fissures
(40-86%)
- Rib destruction in 20% (in advanced
disease)
- Ascites (peritoneum involved in 35%)
- CT
- Pleural thickening (92%)
- Thickening of interlobar fissure (86%)
- Pleural effusion (74%)
- Contraction of affected hemithorax
(42%):
- Ipsilateral mediastinal shift
- Narrowed intercostal spaces
- Elevation of ipsilateral hemidiaphragm
- Calcified pleural plaques (20%)
Circumferentially thickened rind of nodular
pleura with large effusion
- MR (best modality to determine
resectability)
- Minimally hyperintense relative to
muscle on T1WI
- Moderately hyperintense relative to
muscle on T2WI
- Metastases to:
- Ipsilateral lung (60%)
- Hilar and mediastinal nodes
- Contralateral lung and pleura (rare)
- Extension through chest wall and
diaphragm
- Prognosis
- 10% of occupationally exposed
individuals die of mesothelioma (in 50% pleural + in 50%
peritoneal mesothelioma)
- Mean survival time of 5-11 months
- DDx
- Pleural fibrosis from infection (TB,
fungal, actinomycosis)
- Fibrothorax
- Empyema
- Metastatic adenocarcinoma
- Diagnosis
- Video-assisted
thoracoscopic surgery (postprocedural
radiation therapy of all entry ports for tumor seeding of
needle track [21%])
Dahnert 4th
edition
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