High-risk features: history of smoking, family history of lung cancer, emphysema on CT, upper lobe location, spiculated margins. Low-risk = none of these. These guidelines do NOT apply to screening CT (use Lung-RADS instead).
Solid Nodules
| Morphology | Size | Low Risk | High Risk |
|---|---|---|---|
| Single solid | <6 mm (<100 mm³) | No routine follow-up | Optional CT at 12 mo |
| Single solid | 6–8 mm (100–250 mm³) | CT at 6–12 mo, then 18–24 mo if stable | CT at 6–12 mo, then 18–24 mo if stable |
| Single solid | >8 mm (>250 mm³) | CT at 3 mo, PET/CT, or tissue sampling | CT at 3 mo, PET/CT, or tissue sampling |
| Multiple solid | <6 mm | No routine follow-up | Optional CT at 12 mo |
| Multiple solid | ≥6 mm (dominant nodule) | CT at 3–6 mo, then consider CT at 18–24 mo if stable | CT at 3–6 mo, then consider CT at 18–24 mo if stable |
Subsolid Nodules
| Morphology | Size | Recommendation |
|---|---|---|
| Single pure GGO | <6 mm | No routine follow-up |
| Single pure GGO | ≥6 mm | CT at 6–12 mo to confirm persistence; if persistent, CT every 2 yr until 5 yr |
| Single part-solid | <6 mm | No routine follow-up |
| Single part-solid | ≥6 mm | CT at 3–6 mo to confirm persistence; if stable and solid component <6 mm, annual CT for 5 yr; if solid component ≥6 mm, consider PET/CT or tissue sampling |
| Multiple subsolid | Any | CT at 3–6 mo; if stable, manage based on most suspicious individual nodule |
Part-solid nodules carry the highest malignancy risk per unit size — the solid component represents invasive adenocarcinoma and should be measured separately. Monitor solid component growth closely. Pure GGOs: most are adenocarcinoma spectrum (AAH → AIS → MIA → invasive). Doubling time <400 days = suspicious for malignancy.
Key Pearls
- Measure the solid component of part-solid nodules separately from the GGO halo
- Transient nodules (<3 months) are almost always infectious or inflammatory — confirm persistence before initiating Fleischner follow-up
- Perifissural nodules — smooth, lenticular, attached to fissure — are almost always intrapulmonary lymph nodes; no follow-up needed regardless of size
- Calcified nodules (dense, central, laminated, or popcorn pattern) = benign; no follow-up
- Spiculated margins, pleural tethering, or satellite nodules — increase suspicion regardless of size
Reference
MacMahon H et al. Guidelines for Management of Incidental Pulmonary Nodules — Fleischner Society 2017. Radiology. 2017;284(1):228–243.