Uncategorized

• What is it:
  • A nodular pattern in the lungs refers to the
  • presence of
    • multiple,
    • discrete nodules
  • visible on imaging.
    • These nodules vary in:
      • Size (micronodules to larger nodules),
      • Distribution (random, centrilobular, perilymphatic), and
      • Character (solid, cavitating, calcified).
    • The underlying causes are
      • diverse,
      • often requiring
        • clinical correlation and
        • further imaging evaluation.
  • Etymology:
    The term “nodular” originates from the Latin word nodulus, meaning “small knot” or “lump,” reflecting the rounded appearance of these findings.
  • AKA:
    Pulmonary nodules.
  • How does it appear on each relevant imaging modality:
    • Chest X-ray:
      • Single or multiple round opacities with defined or ill-defined margins.
      • Nodules may vary in size and distribution across lung fields.
    • Chest CT:
      • Provides detailed assessment of nodules.
      • Parts: Solid, ground-glass, or mixed attenuation.
      • Size: Classified as
        • micronodules (<3 mm),
        • small nodules (3?10 mm), or
        • large nodules (>10 mm).
      • Shape: Typically round or oval, with smooth or irregular edges.
      • Position: Distribution may be
        • random,
        • centrilobular, or
        • perilymphatic.
      • Character:
        • solid
        • ground glass
        • calcified
        • cavitating
        • bronchocentric
        • fat containing
    • MRI:
      • Rarely used but can detect soft-tissue characteristics of nodules.
    • PET-CT:
      • Assesses metabolic activity in nodules, helping differentiate benign from malignant processes.
  • Differential diagnosis:
    • Infection:
      • Granulomatous diseases (e.g., tuberculosis, histoplasmosis).
      • Fungal infections (e.g., aspergillosis, cryptococcosis).
    • Neoplasm:
      • Primary lung cancer.
      • Metastatic disease.
    • Immune-related or inflammatory:
      • Sarcoidosis.
      • Rheumatoid nodules.
    • Infiltrative disorders:
      • Pulmonary amyloidosis (nodular form).
    • Congenital or inherited:
      • Hamartomas (benign lung nodules).
    • Circulatory:
      • Pulmonary talcosis with intravenous drug abuse should be considered in IV drug users presenting with nodular patterns, especially with a history of injecting adulterated substances.
      • Pulmonary arteriovenous malformations.
    • Iatrogenic:
      • Drug-related pulmonary nodules.
  • Recommendations:
    • Evaluate size, attenuation, and borders of nodules.
    • Assess distribution pattern (e.g., random, centrilobular, perilymphatic) to narrow down differential diagnoses.
    • Follow Fleischner Society guidelines for incidental pulmonary nodules.
    • Consider biopsy or advanced imaging (e.g., PET-CT) for nodules with concerning features (e.g., irregular borders, rapid growth, high FDG uptake).
  • Key points and pearls:
    • The distribution and characteristics of nodules provide critical clues to the etiology:
      • Random: Suggests hematogenous spread (e.g., miliary TB, metastases).
      • Centrilobular: Often related to small airway disease or inhalational exposures.
      • Perilymphatic: Associated with sarcoidosis or lymphangitic carcinomatosis.
      • Calcified nodules are often benign but should be further evaluated if atypical.