Lung Tumours

• Lung tumours can be benign or malignant, with carcinomas being the most common malignant type
• Squamous cell carcinoma:

  • Highly associated with exposure to tobacco smoke
  • Genetics also play a role, with chromosome deletions involving tumour suppressor loci like 3p, 9p, and 17p
  • Often present in the bronchus, common in men
  • Precursor lesion is squamous metaplasia or dysplasia (carcinoma in situ)
• Squamous cell carcinoma is histologically recognized by the presence of intercellular bridges and keratinization
• Adenocarcinoma:

  • More at the periphery compared to squamous cell carcinoma
  • Atypical adenomatous hyperplasia is a premalignant lesion that may progress to adenocarcinoma
  • Associated with gain of function mutations in genes like ALK, EGFR, ROS, and MET
  • Different histologic subtypes include acinar, lepidic, papillary, micropapillary, and solid
• Small cell carcinoma:

  • Highly malignant and metastasizing widely
  • Associated with smoking and may show similar features with squamous cell carcinoma
  • Shows amplification of the MYC gene family
  • Histologically, small cells with scant cytoplasm, ill-defined borders, finely granular nuclear chromatin, and inconspicuous nucleoli
• Large cell carcinoma is an undifferentiated malignant epithelial tumour that lacks the cytological features of other forms of lung cancer