Approach to Solitary Pulmonary Nodule

Initial Characterization and Triage

The American College of Radiology recommends that nodules with benign calcification patterns, such as diffuse, central, laminated, or popcorn calcification, require no further investigation 1
The American Thoracic Society suggests that typical perifissural or subpleural nodules, which are 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 1
The Fleischner Society guidelines state that nodules <5 mm in diameter or <80 mm³ in volume do not require follow-up 1
Solid nodules stable for ≥2 years on comparison imaging are very likely benign and require no further evaluation, according to the European Respiratory Society 2, 3

The Brock model, a validated prediction model, should be used for initial risk assessment, particularly in smokers or former smokers aged ≥50, as recommended by the National Comprehensive Cancer Network 1
Key clinical risk factors to incorporate into the Brock model include increasing age, smoking history and pack-years, and previous malignancy, as suggested by the American Association for Thoracic Surgery 1
Key radiological risk factors include increasing nodule diameter, spiculation, pleural indentation, and upper lobe location, according to the Society of Thoracic Radiology 1, 6

Bronchoscopy is the appropriate test for centrally located tumors, achieving pathological diagnosis in ~90% of cases via forceps biopsy, bronchial brushing, or washing, as recommended by the American College of Chest Physicians 2
Percutaneous CT-guided biopsy is usually appropriate for peripheral lesions ≥8 mm when results will alter management, according to the Society of Interventional Radiology 1
Advanced bronchoscopic techniques, such as radial EBUS or navigational CT-guided bronchoscopy, may be used for peripheral lesions, as suggested by the American Thoracic Society 2

Part-solid nodules ≤8 mm should be followed with CT surveillance at 3, 12, and 24 months, followed by annual CT for 1-3 additional years, as recommended by the Fleischner Society 1
Part-solid nodules >8 mm should be evaluated with repeat CT at 3 months, then proceed to PET, nonsurgical biopsy, and/or surgical resection for persistent nodules, according to the National Comprehensive Cancer Network 1

The American College of Radiology warns against relying solely on nodule size without considering morphology, such as spiculation or upper lobe location, as this leads to underestimation of malignancy risk 6
The Society of Thoracic Radiology advises against delaying evaluation of highly suspicious features, such as spiculated nodules >8 mm, waiting for growth documentation, as this allows disease progression 6
The American Association for Thoracic Surgery recommends against using PET-CT for nodules <8 mm, as sensitivity is inadequate 1
The European Respiratory Society suggests that in Asian populations, PET-CT should not be over-relied upon due to high false-positive rates from endemic granulomatous diseases 7, 3