Management is defined by nodule type (solid vs subsolid), number (single vs multiple), size (average diameter rounded to the nearest millimetre), and overall malignancy risk.

Solid nodules	Scenario	Recommended follow-up
Single, low risk	< 6 mm	No routine follow-up.
Single, low risk	6–8 mm	CT at 6–12 months, if stable, consider CT at 18–24 months.
Single, any risk	> 8 mm	Consider CT at about 3 months, PET/CT and/or tissue sampling.
Single, high risk	< 6 mm	Optional CT at 12 months.
Single, high risk	6–8 mm	CT at 6–12 months, then at 18–24 months.
Multiple, low risk	All < 6 mm	No routine follow-up.
Multiple, low risk	Any 6–8 mm or > 8 mm	CT at 3–6 months, if stable, consider CT at 18–24 months.
Multiple, high risk	All < 6 mm	Optional CT at 12 months.
Multiple, high risk	Any ≥6 mm	CT at 3–6 months, then at 18–24 months.

Subsolid nodules	Scenario	Recommended follow-up
Single ground-glass	< 6 mm	No routine follow-up, in selected high-risk patients consider CT at 2 and 4 years.
Single ground-glass	≥6 mm	CT at 6–12 months to confirm persistence, then every 2 years until 5 years.
Single part-solid	< 6 mm	No routine follow-up in most cases.
Single part-solid	≥6 mm	CT at 3–6 months to confirm persistence, if unchanged and solid component < 6 mm, annual CT for 5 years.
Multiple subsolid	All < 6 mm	CT at 3–6 months, if stable, consider CT at 2 and 4 years.
Multiple subsolid	At least one ≥6 mm	CT at 3–6 months, subsequent management based on the most suspicious nodule.

Fleischner Society Guidelines for Incidental Pulmonary Nodules