What are the follow-up and further evaluation recommendations for lung nodules based on the Fleischer criteria after a computed tomography (CT) scan of the chest?

Management of Lung Nodules Using Fleischner Criteria

You need to follow a risk-stratified, size-based approach that depends on whether your nodule is solid or subsolid (ground-glass), the nodule size, your risk factors for lung cancer, and whether you have single or multiple nodules. 1

First Step: Ensure Proper CT Technique

Before any management decisions can be made, verify that your CT scan meets technical requirements:

• Your CT must be reconstructed with thin sections (≤1.5 mm, typically 1.0 mm) to accurately characterize and measure the nodule 1
• Coronal and sagittal reconstructions should be available to distinguish nodules from scars 1
• Thick sections prevent accurate assessment and should not be used for nodule evaluation 1

Second Step: Determine Your Risk Category

High-risk features include: 1

• Smoking history
• Age ≥65 years
• Family history of lung cancer
• Prior malignancy
• Upper lobe nodule location
• Spiculated or irregular nodule margins
• Presence of emphysema (which independently increases lung cancer risk 3-fold) 2

Third Step: Identify Benign Nodules That Need No Follow-Up

Stop here if your nodule has these benign characteristics: 1

• Smoothly marginated nodules with internal fat and calcification (hamartoma)
• Central, laminar, diffuse, or "popcorn" calcification patterns (healed granulomas)

Fourth Step: Follow Management Based on Nodule Type and Size

For Solid Nodules:

Low-Risk Patients: 1

• <4 mm: No routine follow-up required (malignancy risk <1%)
• 4-6 mm: Optional CT at 12 months
• 6-8 mm: CT at 6-12 months, then at 18-24 months

High-Risk Patients: 1

• <4 mm: Optional CT at 12 months
• 4-6 mm: CT at 3-6 months, then at 18-24 months
• 6-8 mm: CT at 3-6 months, then at 18-24 months

For Pure Ground-Glass Nodules (Subsolid Without Solid Component):

• <6 mm: No routine follow-up required 3, 1
• ≥6 mm: CT at 6-12 months to confirm persistence; if persistent, perform annual CT for 5 years 1

The Fleischner Society specifically recommends annual surveillance for at least 3-5 years for larger nonsolid lesions because these can have extremely slow growth rates (volume doubling times of 400-1,500 days). 3

For Part-Solid Nodules (Ground-Glass With Solid Component):

• <6 mm: No routine follow-up required 1
• ≥6 mm: CT at 3-6 months to confirm persistence; if unchanged and solid component remains <6 mm, perform annual CT for 5 years 1

Part-solid nodules that persist beyond 3 months should be considered malignant until proven otherwise, especially when the solid component measures >5 mm. 3

For Multiple Nodules:

Low-Risk Patients: 1

• Small nodules: No routine follow-up
• Larger nodules: CT at 3-6 months, then consider CT at 18-24 months

High-Risk Patients: 1

• Small nodules: Optional CT at 12 months
• Larger nodules: CT at 3-6 months, then at 18-24 months

Critical Technical Points for Follow-Up:

• All surveillance CT scans should use noncontrast techniques with thin sections through the nodule 3
• Measurement of subsolid nodules is challenging due to indistinct margins and measurement error 3
• Any nodule that grows or develops a solid component is often malignant and requires further evaluation or consideration of resection 3, 1

Important Caveats:

Avoid PET scans and needle biopsies for most subsolid nodules, as they have limited utility; however, PET may be considered for part-solid nodules ≥8 mm 3

If you have life-limiting comorbidities where a low-grade malignancy would be of little consequence, limited duration or no follow-up may be preferred 3

Do not confuse ground-glass opacities with emphysema on imaging—they require completely different evaluation and follow-up protocols 2