lung cancer | Anatomy2Medicine
lung-cancer Causes

lung cancer

 

  • Bronchogenic carcinoma
      • Most lung tumors are malignant
      • metastases from primary tumors elsewhere occur more frequently than those that originate in the lung
  • It is increasing in incidence, especially in women, in parallel with cigarette smoking.
      • it is directly proportional in incidence to the
        • number of cigarettes smoked daily
        • number of years of smoking.
      • Various histologic changes that precede bronchogenic carcinoma in cigarette smokers.
        • squamous metaplasia of the respiratory epithelium
        • atypical changes ranging from dysplasia to carcinoma in situ
      • Other etiopathogenic factors
        • Air pollution
        • Radiation; incidence increased in radium and uranium workers
  • Asbestos (MCQ)
        • increased incidence with asbestos and greater increase with combination of asbestos and cigarette smoking (MCQ)
        • Industrial exposure to nickel and chromates (MCQ)
      • Clinical features
        • The 5-year survival rate is less than 10%.
  • The tumor often spreads by local extension into the pleura, pericardium, or ribs.
  • Clinical manifestations
  • cough, hemoptysis
          • bronchial obstruction, often with atelectasis and pneumonitis.
          • Superior vena cava syndrome
            • compression or invasion of the superior vena cava
            • result in facial swelling and cyanosis
            • dilation of the veins of the head, neck, and upper extremities
          • Pancoast tumor (superior sulcus tumor); (MCQ)
            • involvement of the apex of the lung
            • often with Horner syndrome (ptosis, miosis, and anhidrosis)
            • involvement of the cervical sympathetic plexus
          • Hoarseness from recurrent laryngeal nerve paralysis
          • Pleural effusion, often bloody
            • bloody pleural effusion suggests malignancy, tuberculosis, or trauma.
          • Paraneoplastic endocrine syndromes
            • most frequent is ACTH or ACTH-like activity with small cell carcinoma (MCQ)
            • SIADH with small cell carcinoma of the lung (MCQ)
            • parathyroid-like activity with squamous cell carcinoma. (MCQ)
        • Classification
          • All types share a common endodermal origin despite their morphologic differences.
          • Bronchogenic carcinoma is subclassified into
  • squamous cell carcinoma
  • adenocarcinoma (including bronchioloalveolar carcinoma)
  • small cell carcinoma
  • large cell carcinoma
          • For therapeutic purposes, the bronchogenic carcinomas are often subclassified into
  • small cell carcinoma, which is not considered amenable to surgery
  • non-small cell carcinoma, in which surgical intervention may be considered.
  • Clinical Pearls on Brocnchogenic carcinoma – Very High yielding for USMLE, MD Entrance and MBBS Exams
  • Squamous cell carcinoma
  • Central
      • Appears as a hilar mass (MCQ)
      • frequently results in cavitation
      • clearly linked to smoking
      • incidence greatly increased in smokers
      • may be marked by inappropriate parathyroid hormone (PTH)–like activity with resultant hypercalcemia(MCQ)
  • Adenocarcinoma carcinoma
      • Bronchial-derived
  • Peripheral
  • Develops on site of prior pulmonary inflammation or injury (scar carcinoma) (MCQ)
      • less clearly linked to smoking
  • Bronchioloalveolar carcinoma
  • Peripheral (MCQ)
      • Less clearly related to smoking
  • columnar-to-cuboidal tumor cells line alveolar walls
      • presents with multiple densities on x-ray, mimicking pneumonia(MCQ)
  • Small cell (oat cell) carcinoma
      • Central
      • Undifferentiated tumor
      • most aggressive bronchogenic carcinoma (MCQ)
      • least likely form to be cured by surgery(MCQ)
      • usually already metastatic at diagnosis
  • often associated with ectopic production of corticotrophin (ACTH) or
  • antidiuretic hormone (ADH) (MCQ)
      • incidence greatly increased in smokers (MCQ)
  • Large cell carcinoma
  • Peripheral (MCQ)
      • Undifferentiated tumor
      • may show features of squamous cell or adenocarcinoma on electron microscopy
  • Carcinoid tumor
    • Arise from major bronchi
    • Low malignancy (MCQ)
    • spreading by direct extension into adjacent tissues
    • may result in carcinoid syndrome (MCQ)