Lung nodule and lung mass

Lung anatomy
- Primary lung lobule
  - Not so important in radiology
- Secondary lung lobule
  - Represent a cluster of up to 30 acini supplied by a common distal pulmonary artery and bronchiole
  - Have polyhedral shape
  - Bounded by intralobular septa
    - Are visible as Kerley B lines in pulmonary oedema
Lung mass < 3 cm = nodule
Lung mass > 3 cm = mass
Modalities
- X-ray
- CT
- PET
Benign vs malignant
- Characteristics of benign masses
  - Age < 40
  - Small (< 3 cm)
  - Round
  - Well-defined edges
  - Slow growth over time (years)
    - Comparison with older images is important!
  - Solid
  - Central, laminar or diffuse calcification
- Characteristics of malignant masses
  - Age > 40
  - Large (> 3 cm)
  - Irregular shape
  - Poorly defined edges
  - Obvious growth over time
  - Cavitated
  - Active accumulation of FDG on PET scan
Indirect signs of lung mass
- Atelectasis
- Postobstructive pneumonia
- Pleural effusion
- Hilar adenopathy
High risk
- Smoker
- > 40 years
- Clinical symptoms suspicious of cancer
  - Haemoptysis
  - Weight loss
  - Hoarseness
- Mass has malignant characteristics on imaging
If mass and/or patient is high risk -> investigation
- CT
  - Also for small peripheral lung masses
- PET
- Biopsy
Differential diagnosis
- Granuloma
  - TB
  - Histoplasmosis
- Hamartoma
- Primary lung cancer
  - Usually solitary nodule
  - Adenocarcinoma
    - Peripheral mass
  - Squamous cell carcinoma
    - Central mass
  - Small cell carcinoma
    - Hilar mass
- Metastases
  - Usually multiple nodules
- Round pneumonia
If tumor in apex of lung = Pancoast tumor
Multiple lung nodules must always be examined with CT

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