see also:

• lung cancer

• lung lesions are often found incidentally on CXRs or CT scans ordered by GPs or in the ED
• TB and lung cancers are common and need to be excluded or followed up appropriately when suspicion arises
  • see Ann Thorac Med 2019 Lung nodules: A comprehensive review on current approach and management

• tuberculosis (TB)
• lung cancer
• abscess

• a bronchogenic carcinoma (mostly squamous cell or adenocarcinoma) arising at the apex of the lung and tends to invade adjacent soft tissue and bone
• may cause:
  • local or radiated pain to shoulder/hand
  • Horner's syndrome
  • neuropathic weakness of ipsilateral hand

• benign tumours
  • suggested by (but cannot exclude a malignancy):
    • calcification especially if either:
      • diffusely present within the nodule
      • mainly central
      • multiple large areas of calcification
      • rings of calcification (laminar)
    • very fast (double size in less than 1 month) or very slow growth rate much the same in 2 years (lung cancers tend to grow slowly)
    • small size
    • smooth outer margins
    • if cavitating, then maximal wall thickness < 4mm (over 95% are benign such as an abscess)
  • hamartoma
    • usually well-circumscribed nodules often with multiple large areas of calcification “popcorn”
    • finding areas of fatty tissue (−40 to −120 HU) makes it highly likely
  • carcinoid tumour - 85% of benign pulm. tumours, but < 3% have carcinoid syndrome
  • etc
• lung cancer
  • suggested by:
    • risk factors for lung cancer eg. older patient, past or current smoker, industrial exposures, etc
    • larger size
    • spiculated margins or lobulated contour
    • enhancement characteristics with IV contrast
    • pleural retraction (visceral pleura pulled towards the nodule)
    • growth rate:
      • solid cancers generally doubles in volume over between 100 and 400 days, while subsolid cancers (generally representing adenocarcinomas) generally doubles in volume over 3 to 5 years (a volume doubling equates to a 26% increase in diameter)
    • if cavitating, then maximal wall thickness > 16mm (90% are malignant - usually squamous cell lung cancer as small cell lung cancer rarely cavitates)
    • mediastinal lynphadenopathy
      • extensive lymphadenopathy is seens with small cell carcinoma lung, lymphoma, leukaemia, and metastases from renal cell Ca, melanoma and testicular cancer
  • bronchogenic carcinomas most commonly are seen in upper lobes esp. anterior segment with a R:L ratio of 3:2
  • squamous cell lung cancers generally present as a central mass +/- atelectasis / post-obstructive pneumonia, while 30% cavitate
  • adenocarcinoma tends to present as a peripheral nodule or mass, and should be considered in apparent pneumonic changes which fail to resolve
  • small cell carcinoma usually present as a central mass (80% cases) with extensive mediastinal lymphadenopathy
  • large cell carcinoma tends to present as a large peripheral mass
  • NB. a new solitary pulmonary nodule in a patient with an extra-thoracic primary neoplasm usually represents a new primary lung cancer unless the primary is a melanoma or sarcoma in which case a solitary metastasis is more likely
  • NB. synchronous multiple lung cancers are uncommon in < 5%
    • but tend to be a feature of rare primary lung neoplasms that originate from epithelial (pneumocytes and neuroendocrine), mesenchymal (vascular and meningothelial) and lymphoid tissues of the lung ¹⁾
  • 10-15% of patients treated for lung cancer develop a new lung cancer with average time interval of ~5 years
  • metastatic tumours to the lung are generally spread via pulmonary arteries and thus tend to occur in lower zones of the lungs, and tend to be peripheral (90% are in outer 1/3rd)
• rare:
  • parasites such as:
    • Ascaris (adult small bowel→larvae lungs)
    • Ancylostoma & Necator (hookworms) (skin→lung→duodenum)
    • strongyloidiasis
    • angiostrongyliasis
    • Paragonimus (raw crustaceae ingested→adults in lung)
    • Dirofilaria from mosquitoes

• larger than 3cm diameter
• round pneumonia
• other infections
  • lung abscess
  • Q fever
  • hydatid cyst
  • etc
• lung cancer
• etc

• pleural plaques from asbestosis
• sarcoidosis
• past granulomatous infection
• infections
• metastatic cancers to the lungs - usually in outer 1/3rd and in lower zones
• miliary TB
• synchronous lung cancers (uncommon)