Exclusions — algorithm does not apply:
- Lung cancer screening programs (use Lung-RADS)
- Recent history of malignancy (use clinical judgment; short-term 1–6 month follow-up based on tumor histology)
- Unexplained fever or symptoms referable to the nodule
- Age <35 years (management depends on clinical scenario)
- Limited life expectancy or comorbidities that make treatment riskier than the suspected malignancy
Risk Stratification
Low risk (<5% malignancy): younger age, never/light smoker, smooth regular margins, non–upper lobe location.
High risk (≥5% malignancy): older age, heavy smoker, spiculated or lobulated margins, upper lobe location. The PanCan (Vancouver) model provides the best validated risk estimate for small nodules.
Size = average of long- and short-axis diameters, measured on thin-section (≤1.5 mm) reconstructions. Follow-up CT should be noncontrast, low-dose technique.
Single Solid Nodule
| Risk | <6 mm | 6–8 mm | >8 mm |
|---|---|---|---|
| Low risk (<5%) | No further workup | CT at 6–12 mo; consider CT at 18–24 mo | CT at 3 mo, or PET/CT and/or tissue sampling |
| High risk (≥5%) | Optional CT at 12 mo | CT at 6–12 mo; then CT at 18–24 mo | CT at 3 mo, or PET/CT and/or tissue sampling |
Multiple Solid Nodules
Assess by the largest or most concerning nodule. Follow-up intervals may vary according to size and risk.
| Risk | <6 mm | 6–8 mm | >8 mm |
|---|---|---|---|
| Low risk (<5%) | No further workup | CT at 3–6 mo; consider CT at 18–24 mo | CT at 3–6 mo; consider CT at 18–24 mo |
| High risk (≥5%) | Optional CT at 12 mo | CT at 3–6 mo; then at 18–24 mo | CT at 3–6 mo; then at 18–24 mo |
Subsolid Nodules — GGO and Part-Solid
| Size | Number | Type | Management |
|---|---|---|---|
| <6 mm | Solitary | GGO or part-solid | No further workup |
| <6 mm | Multiple | Any subsolid | CT at 3–6 mo; if unchanged → consider CT at 2 and 4 years |
| ≥6 mm | Solitary | Pure GGO | CT at 6–12 mo to confirm persistence; if unchanged → CT every 2 years until 5 years; if solid component develops or growth → consider resection |
| ≥6 mm | Solitary | Part-solid | CT at 3–6 mo to confirm persistence; if solid component <6 mm and unchanged → annual CT ≥5 years; if solid component ≥6 mm or enlarging → consider resection |
| ≥6 mm | Multiple | Any subsolid | CT at 3–6 mo; subsequent management based on most suspicious nodule |
Perifissural nodules: Smooth oval, lentiform, or triangular shape abutting a fissure — almost always benign intrapulmonary lymph nodes. No follow-up CT recommended if ≤10 mm with typical morphology.
Multiple <6 mm pure GGOs: Usually benign; consider follow-up CT at 2 and 4 years in selected high-risk patients.
Reporting Elements
- Size — average long- and short-axis diameter in mm (thin-section images, lung windows)
- Number — solitary vs. multiple
- Density — solid, part-solid, pure GGO; if part-solid, measure the solid component separately
- Morphology — margin characteristics (smooth, lobulated, spiculated); calcification pattern (benign patterns: central nidus, laminated, popcorn, diffuse); fat attenuation
- Location — lobe, relationship to pleura/fissures
References
Munden RF, Black WC, Hartman TE, et al. Managing Incidental Findings on Thoracic CT: Lung Findings. A White Paper of the ACR Incidental Findings Committee. J Am Coll Radiol. 2021;18(9):1267–1279.
MacMahon H, Naidich DP, Goo JM, et al. Guidelines for Management of Incidental Pulmonary Nodules Detected on CT Images: From the Fleischner Society 2017. Radiology. 2017;284(1):228–243.