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Fleischner Society Guidelines for Incidental Pulmonary Nodules
Follow-up imaging recommendations for an incidentally found pulmonary nodule on CT.
Fleischner Society Guidelines for Incidental Pulmonary Nodules
Nodule type
Solid nodules obscure the underlying lung parenchyma on CT; ground-glass nodules do not; part-solid nodules have both a solid and a ground-glass component.
Number of nodules
Average diameter of the (most suspicious) nodule
mm
Patient risk category (applies to solid nodules)
High risk: heavy smoking history, older age, family history of lung cancer, emphysema/fibrosis, nodule with upper-lobe location or spiculated margins. Low risk: absence of these factors.
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When to use
- Determining an appropriate follow-up CT interval for a pulmonary nodule found incidentally on chest CT in an adult 35 years or older.
- Not intended for lung cancer screening cohorts (use Lung-RADS instead), or for nodules in patients under 35, with known primary malignancy, or who are immunocompromised.
Formula
Decision tree by nodule type (solid, part-solid, or pure ground-glass), multiplicity (single vs multiple), size (below 6 mm, 6-8 mm, or above 8 mm for solid nodules; below vs at/above 6 mm for subsolid nodules), and, for solid nodules only, patient risk category (low vs high). For multiple subsolid nodules, the size threshold (below vs at/above 6 mm) drives the recommendation regardless of whether the nodules are part-solid or pure ground-glass. Each combination maps to a specific no-follow-up, interval-CT, or further-workup (PET/CT or tissue sampling) recommendation.
Pearls and pitfalls
- Risk stratification (low vs high risk) changes management only for solid nodules; subsolid nodule follow-up does not depend on risk category in the 2017 guideline.
- A solid nodule 8 mm or larger warrants consideration of PET/CT or tissue sampling rather than routine surveillance alone.
- Part-solid nodules with a persistent solid component carry the highest malignancy risk among subsolid nodules and merit prolonged annual surveillance.
- Multiple subsolid nodules under 6 mm are NOT exempt from follow-up: because of the risk of multifocal, synchronous adenocarcinomas, they still merit CT at 3-6 months with consideration of CT at 2 and 4 years if stable.