Lung Cancer

Pathophysiology

Squamous cell – 1) arises in central part of lung 2) derives from repeatedly injured bronchial lining 3) ulcerates into lung parenchyma 4) most common subtype that forms Pancoast tumor in apex of lung 5) metastases go to hilar and mediastinal lymph nodes, adrenals, and other sites Adenocarcinoma – 6) can arise anywhere but typically distal 7) most common tumor in nonsmokers Large cell – 8) poorly differentiated and can occur anywhere in lung Small cell – 9) fast-growing with early metastases 10) presents usually as perihilar mass 11) most common subtype causing paraneoplastic syndromes

Signs and Symptoms

1) dyspnea 2) cough 3) chest pain 4) hemoptysis 5) obstructive pneumonia 6) lobar collapse 7) pleural effusions 8) weight loss

Characteristic Test Findings

Laboratory – 1) hypercalcemia (squamous cell) 2) ectopic ACTH production (small cell) Radiology – 3) large opaque mass on chest radiograph (usual test of diagnosis)

Histology/Gross Pathology

main histologic subtypes are small cell and non-small cell (squamous, adenocarcinoma and its subtype bronchoalveolar, and large cell)

Associated Conditions

Squamous cell – 1) Pancoast’s tumor 2) Horner’s syndrome 3) superior vena cava syndrome 4) hypercalcemia Small cell – 5) diabetes insipidus 6) Cushing’s syndrome 7) Eaton-Lambert syndrome

Biochemistry

1) k-ras mutations (non-small cell) 2) myc mutations (small cell) 3) p53 and retinoblastoma (RB) mutations (both small cell and non-small cell)

Inheritance/Epidemiology

1) most common cause of cancer death in both men and women in USA 2) peak age of presentation is 60-70 years

Treatment

1) small cell – chemotherapy (very responsive but palliative only) 2) non-small cell resection – resection for cure, if possible, with chemoradiation 3) superior vena caval syndrome – urgent radiation to shrink tumor and decompress venous drainage

Tips for USMLE

1) adenocarcinoma can occur in nonsmokers 2) if a 69 year-old man who has smoked two packs of cigarettes for 50 years has noticed a worsening of his chronic cough, new onset blood-streaked sputum and a 20 pound weight loss over the past two months, think lung cancer