Nodules can be categorised in several ways with the most important one being the distribution within the secondary lobule. This distribution is essential for the accurate diagnosis of the nodular pattern. Nodules can be distributed in three different ways:


  • Present in the interlobular septa, pleural surfaces, and the bronchovascular sheath
  • Most commonly seen in sarcoidosis or neoplasm


  • Present only in the centrilobular region, spaced 5-10 mm from the pleura and up to 1 cm in size, although not necessarily in the centres of the secondary lobules, the pleural surfaces are spared
  • Can appear in rosettes or be diffuse
  • Not necessarily disease-related


  • Randomly distributed relative to structures of the secondary lobule throughout the lung parenchyma
  • Can be associated with haematogenous metastases, miliary tuberculosis, miliary fungal infections, or Langerhans cell histiocytosis (early nodular stage)