Asbestos-Related Lung Disease (mesothelioma)

Question 1

Definition

Answer 1

• Aggressive tumour of mesothelial cells that usually occurs in the pleura (90%), and sometimes in peritoneum, pericardium or testes
• Aggressive epithelial neoplasm arising from the lining of the lung, abdomen
(peritoneum), pericardium or tunica vaginalis

• Mesothelium = simple squamous epithelium that makes up the pleura, peritoneum, mediastinum and pericardium that line the body cavities

Question 2

Aetiology

Answer 2

• Caused by exposure to ASBESTOS but the relationship is complex
• Dose-response relationship – increased cumulative exposure increases risk

• 90% report previous exposure to asbestos, but only 20% of patients have pulmonary asbestosis
• The latent period between exposure and development of tumour can be up to 45
years

• Malignant pleural mesothelioma rarely spreads to distant sites but most patients present with locally advanced disease.
• Other causes: radiation, genetic predisposition (germline mutations), simian virus 40 (an oncogenic virus)

Question 3

Epidemiology

Answer 3

• Mesothelioma is rare – more common in elderly

• Asbestos exposure is documented in 90% of cases
• Latent period between exposure and mesothelioma = 20-40 years (up to 50 yrs), therefore most pts are older adults (60-85 years)
• More common in MALES and WHITE people – reflects occupational exposure
• Poor prognosis

Question 4

Presenting symptoms

Answer 4

• Most common symptoms: SOB, Chest pain (dull, diffuse, developing), weight loss
o SOB – typically due to large pleural effusion or trapped lung

• Cough – dry, non-productive
• FLAWS
• Bone pain

• Abdominal pain/distension – may extend to abdo cavity → ascites
o Late presentation of pleural mesothelioma
o Often presenting symptom of peritoneal mesothelioma

• Sometimes, bloody sputum (haemoptysis) – if tumour invades blood vessel

Question 5

Signs on physical examination

Answer 5

• Occasional palpable chest wall mass
• Finger clubbing – due to underlying asbestosis (pulmonary fibrosis)

• Recurrent pleural effusions
o Reduced breath sounds
o Stony dull percussion

• Signs of metastases: Lymphadenopathy, Hepatomegaly, bone tenderness
• Abdominal pain/obstruction (peritoneal malignant mesothelioma)
• Can rarely cause pneumothorax

Question 6

Investigations (CXR and CT)

Answer 6

CXR/CT: irregular pleural thickening, pleural effusion, bloody pleural fluid

o Reduced lung volumes, parenchymal changes related to asbestos exposure eg lower zone liner interstitial fibrosis (ie asbestosis)
o May show pleural mass and rib destruction
o CT can show enlarged mediastinal (and hilar) lymph nodes and chest wall invasion

o CT is better – CXR visualises pleura poorly and will miss subtle abnormalities and does not assess mediastinal lymph nodes

o MRI and PET – can distinguish benign from malignant but not as good as biopsy, PET can see mets/spread