Uncategorized

• What is it:
  • Subpleural nodules in the lungs refer to:
    • the presence of:
      • multiple or solitary nodules,
      • located immediately adjacent to the pleura,
      • including the fissures.
  • These nodules are commonly associated with:
    • inflammatory,
    • infectious,
    • neoplastic, or
    • lymphatic processes.
• Etymology:
  • Derived from the Latin sub- (under or beneath) and pleura (side or rib), describing nodules beneath the pleural surface.
• AKA:
  • Pleural-adjacent nodules.
• How does it appear on each relevant imaging modality:
  • Chest X-ray:
    • Subtle or indistinct opacities near the pleura.
    • Better visualized with lateral or oblique views if nodules are small.
  • Chest CT:
    • Parts: Nodules located immediately adjacent to the pleural surfaces, including interlobar fissures.
    • Size: Varies from micronodules (<3 mm) to larger nodules (>10 mm).
    • Shape: Round or oval; may appear irregular depending on the cause.
    • Position:
      • Adjacent to pleural surfaces or fissures, predominantly peripheral in location.
    • Character:
      • May appear solid, calcified, or associated with ground-glass opacity.
      • Cavitation is less common  but may occur in certain conditions (e.g., septic emboli infection or malignancy).
    • Time:
      • Subpleural nodules may evolve, resolve (e.g., infections), or grow (e.g., malignant or progressive inflammation).
  • MRI:
    • Rarely used but may demonstrate hyperintensity on T2-weighted images if inflammation or edema is present.
  • PET-CT:
    • Recommended for lesions larger than 7 mm.
    • Identifies:
      • Active lesions with increased metabolic activity (e.g., malignant or acute inflammation/infection).
      • Cold lesions with low metabolic activity (e.g., chronic inflammation or paucicellular neoplasms).
• These nodules reflect:
  • Pleural-adjacent pathology:
    • Inflammation:
      • Hypersensitivity pneumonitis.
      • Rheumatoid nodules.
    • Infection:
      • Tuberculosis with subpleural involvement.
      • Fungal infections (e.g., aspergillosis, histoplasmosis).
    • Lymphatic involvement:
      • Sarcoidosis (perilymphatic distribution).
      • Lymphangitic carcinomatosis.
    • Neoplastic processes:
      • Subpleural metastases.
• Differential diagnosis:
  • Infection:
    • Tuberculosis (primary or post-primary with subpleural focus).
    • Fungal infections (e.g., coccidioidomycosis, histoplasmosis).
  • Inflammation:
    • Sarcoidosis (early or chronic stages).
    • Hypersensitivity pneumonitis (subpleural micronodules).
  • Neoplasm:
    • Subpleural metastases (e.g., breast cancer, melanoma).
    • Pleural-based primary tumors (e.g., mesothelioma).
  • Inhalational exposure:
    • Pneumoconioses (e.g., silicosis, asbestosis with subpleural fibrosis).
  • Immune-related:
    • Rheumatoid nodules.
  • Iatrogenic:
    • Post-radiotherapy nodules.
  • Circulatory:
    • Pulmonary infarcts adjacent to the pleura.
• Recommendations:
  • Perform high-resolution CT to define the size, position, and morphology of subpleural nodules.
  • Bronchoscopy or biopsy if malignancy or granulomatous diseases are suspected.
  • PET-CT to differentiate between active and cold lesions for nodules larger than 7 mm.
  • Monitor with follow-up imaging for changes in size or character over time.
• Key points and pearls:
  • Subpleural nodules are often associated with pleural or lymphatic processes.
  • Nodules along fissures may suggest perilymphatic spread (e.g., sarcoidosis or metastases).
  • Calcified nodules are typically benign (e.g., healed granulomas).
  • Subpleural positioning and time-dependent changes (e.g., growth, resolution) are critical for diagnosis and management.