Fleischner guidelines

Fleischner is a recommendation framework, not a category lexicon: it does not output a number or grade. Instead, the radiologist locates a nodule along several axes — its type (solid versus subsolid, with subsolid split into pure ground-glass and part-solid), its size, whether it is single or multiple, and the patient's risk level (low versus high) — and arrives at a suggested follow-up action. The precise size thresholds and recommended intervals should be read directly from the official 2017 Radiology paper.

• No routine follow-upFor the smallest or clearly low-risk nodules, where the chance of cancer is negligible (also typical benign patterns such as perifissural nodules).
• Optional / discretionary follow-up CTBorderline or indeterminate cases where a repeat scan may be considered but is not mandatory.
• Definite surveillance CTA recommended repeat CT (sometimes a sequence over time) to confirm stability or detect growth.
• Further workup / consider tissue samplingFor larger or more suspicious nodules, escalation toward PET-CT, biopsy, or specialist referral.

These are our plain-language summaries. For the exact criteria, thresholds, and management rules, see the official source.

Fleischner and Lung-RADS are complementary, not competing: Fleischner handles nodules found by chance on a non-screening CT, while Lung-RADS handles nodules found during organized low-dose CT lung-cancer screening of high-risk people. Fleischner is consensus guidance expressed as follow-up directions, whereas Lung-RADS is a categorical reporting system tied to screening programs. They use different size thresholds and decision logic, so the same nodule can yield different recommendations under each — they should not be substituted for one another. Fleischner also differs from disease-specific or screening guidelines from other bodies (e.g. NCCN, ACCP, BTS).

The 2017 guideline is the most widely cited reference for incidental pulmonary nodules and is broadly endorsed, with an educational companion clarifying its application. Real-world adherence, however, is imperfect: surveys show high awareness but inconsistent conformance when radiologists are tested on actual cases, and more recent data suggest radiologists self-report high adherence yet tend to overestimate how strong the underlying evidence base is. A 2026 comparison with Lung-RADS v2022 reinforced that, for identical solid nodules, the two systems diverge in follow-up timing and biopsy thresholds and are not interchangeable. The principal critiques are interobserver variability in nodule measurement/classification and the risk of both under- and over-follow-up when the guideline is applied loosely.

Is Fleischner a 'RADS' like Lung-RADS or TI-RADS?

No. It is a set of consensus follow-up recommendations from the Fleischner Society, not a numbered category system and not an ACR product.

When do the Fleischner guidelines apply?

To pulmonary nodules found incidentally on a CT done for another reason, in adults from about age 35 up. They do not apply to lung-cancer screening exams.

Who is excluded?

They are not intended for lung-cancer screening, for people with a known or suspected cancer, or for immunocompromised patients — those situations need different pathways.

Does following the guideline mean a nodule is cancer?

No. Most incidental nodules are benign; the recommendation simply tells the care team whether and when to recheck.

Is the 2017 version still current?

Yes, as of 2026. A 2024 Fleischner publication updated thoracic-imaging terminology only and did not change the nodule follow-up recommendations.

Fleischner Society

An independent international thoracic-imaging society that issues consensus statements, including the incidental pulmonary nodule guidelines.

Incidental pulmonary nodule

A lung nodule found unexpectedly on a CT performed for an unrelated reason (not on a screening exam).

Pulmonary nodule

A small, roughly rounded spot in the lung (generally up to about 3 cm; larger lesions are called masses).

Solid nodule

A nodule of uniform soft-tissue density that obscures the lung behind it.

Subsolid nodule

An umbrella term for any nodule containing a hazy ground-glass component (pure ground-glass and part-solid types).

Ground-glass nodule (GGN)

A hazy nodule through which normal lung vessels remain visible, with no solid component.

Part-solid nodule

A nodule with both ground-glass and solid components; it carries the highest cancer risk among nodule types, and the solid part guides management.

• officialFleischner Society 2017 guideline (Radiology / RSNA)
• officialFleischner Society official website (white papers)
• cmeRadioGraphics companion — common questions & scenarios (CME-eligible)
• calculatorMDCalc — Fleischner incidental nodule follow-up calculator (third-party)
• patientAmerican Lung Association — understanding lung nodules (patient)