Lung cancer ****is the third most common cancer in the UK, behind breast and prostate cancer

Aetiology

• Inhalation of carcinogens:
  • Smoking accounts for 80-90% of lung cancers
  • Asbestos - chrysotile fibres most common and account for majority of cases, crocidolite (amphibole) is the most dangerous type due to straight structure
  • Pollution
• HIV
• Organ transplantation
• Radiation exposure (X-ray, gamma rays)
• Beta-carotene supplements in smokers

Pathophysiology

Small cell lung cancer (SCLC) - 25%

• Rapidly progressive disease - early metastases and is almost always inoperable at presentation
• Worst prognosis of all types of lung cancer
• Central tumour
• Associated with ectopic ACTH secretion → Cushing’s
• Associated with SIADH → hyponatremia

Adenocarcinoma - 35%

• Type most likely to be found in non-smokers
• Particularly prevalent in Asian women - one hypothesis links this to a mutation in Epidermal Growth Factor Receptor (EGFR)
• Type most closely linked with asbestos
• Peripheral tumour
• Commonly invades the mediastinal lymph nodes and the pleura, and spreads to the brain and bones