What is the management approach for reticulonodular (reticulo nodules) lesions in the lungs?

Management Approach for Reticulonodular Lesions in the Lungs

The management of reticulonodular lesions in the lungs should follow a risk-stratified approach based on nodule size, characteristics, and patient risk factors, with nodules ≥8 mm or ≥300 mm³ requiring risk assessment using validated prediction models to guide further evaluation. 1

Initial Assessment

• All CT scans of the thorax should be reconstructed with contiguous thin sections (≤1.5 mm, typically 1.0 mm) to enable accurate characterization and measurement of pulmonary nodules 2
• Coronal and sagittal reconstructions should be routinely acquired to facilitate distinction between nodules and scars 2
• Nodules with diffuse, central, laminated or popcorn pattern of calcification or macroscopic fat do not require follow-up or further investigation 2, 1
• Typical perifissural or subpleural nodules (homogeneous, smooth, solid nodules with lentiform or triangular shape within 1 cm of a fissure or pleural surface and <10 mm) do not require follow-up 2, 1
• Nodules <5 mm in maximum diameter or <80 mm³ in volume do not require follow-up 2, 1

Risk Assessment for Nodules ≥8 mm or ≥300 mm³

• Use the Brock model (full, with spiculation) for initial risk assessment, especially in smokers or former smokers aged ≥50 2, 1
• Consider key clinical risk factors including:
  • Increasing age (OR=1.04–2.2 for every 10-year increment) 2
  • Current or former smoking status (OR=2.2–7.9) 2
  • Pack-years of smoking 2
  • Previous history of extrapulmonary cancer 2
• Important radiological risk factors include:
  • Nodule diameter (OR approximately 1.1 for each 1 mm increment) 2
  • Spiculation (OR=2.1–5.7) 2
  • Upper lobe location 2
  • Pleural indentation 2
  • Volume doubling time <400 days 2

Management Algorithm Based on Risk Assessment

For Solid Nodules:

• Low risk (<10% probability of malignancy):

  • CT surveillance is recommended 2, 1
  • For nodules 5-6 mm: CT at 1 year after baseline 2
  • For nodules ≥6 mm: CT at 3 months, then at 1 year if stable 2

• Intermediate risk (10-70% probability of malignancy):

  • PET-CT is recommended for further risk assessment 2, 1
  • Consider image-guided biopsy if PET-CT is positive or inconclusive 2
  • If biopsy is non-diagnostic, consider surgical excision or continued surveillance based on clinical suspicion 2

• High risk (>70% probability of malignancy):

  • Consider excision or non-surgical treatment 2, 1
  • Surgical resection preferentially by video-assisted thoracoscopic surgery (VATS) 2
  • For patients unfit for surgery, consider stereotactic ablative body radiotherapy (SABR) or radiofrequency ablation (RFA) 2

For Sub-solid Nodules:

• Repeat thin section CT at 3 months to confirm persistence 2
• If resolved: no further follow-up 2
• If persistent:
  • Low risk: thin section CT at 1,2, and 4 years from baseline 2
  • Higher risk or concerning morphology: consider image-guided biopsy or resection/non-surgical treatment 2
  • Any change in mass or new solid component warrants further workup 2

Diagnostic Procedures

• PET-CT:

  • Has approximately 97% sensitivity and 78% specificity for nodules ≥1 cm 1
  • Limitations include false-negatives (particularly with adenocarcinoma in situ, carcinoid tumors, and nodules <8 mm) and false-positives (inflammatory conditions) 1

• Image-guided biopsy:

  • Consider for nodules where the result will alter management plan 2, 1
  • Consider risk of pneumothorax when deciding on transthoracic needle biopsy 2
  • Be aware that a negative biopsy does not definitively exclude malignancy - if pre-test probability is high (e.g., 90%), there may still be a 50% chance of malignancy after a negative biopsy 2

• Bronchoscopy:

  • Consider in the evaluation of pulmonary nodules with bronchus sign present on CT 2
  • Consider augmenting yield using radial endobronchial ultrasound, fluoroscopy or electromagnetic navigation 2

Important Differential Diagnoses for Reticulonodular Patterns

• Malignancy (primary lung cancer or metastases) 3
• Infectious causes:
  • Mycoplasma pneumoniae (can present with diffuse reticulonodular shadows and hilar lymphadenopathy) 4
  • Paragonimiasis (can present with reticulonodular lesions and pleural effusion) 5
• Granulomatous inflammation (e.g., post-BCG therapy) 6

Pitfalls to Avoid

• Do not assume coexistent lung nodules in patients with known lung cancer are metastases; evaluate them in their own right 2
• Do not use partial thoracic CT scans for nodule follow-up as this may miss unanticipated abnormal findings 2
• Do not rely solely on manual caliper measurements; volumetric assessment is more accurate for detecting growth 2
• Be aware that the negative predictive value of a biopsy is greatest when the pre-test probability of malignancy is low 2