Fleischner 2017 — ProtoMD

Nodule Parameters

1. Nodule Count

2. Morphology

3. Average Diameter (mm)

Measure mean of long & short axis

4. Clinical Risk Profile

High risk: Smoking history, family history of lung cancer, or spiculated margins.

Enter patient findings to visualize the
recommended follow-up pathway.

Clinical Recommendation

—

Certainty

—

Modality

—

Recommended Follow-Up Schedule

Practical Points & Guideline Notes

📐 Nodule Measurement Technique ▾

Image Production & Viewing

Acquire images in full inspiration
Measure in the axial (transverse) plane; coronal/sagittal if greatest dimensions lie there
Measure in lung windows; soft tissue windows help assess density changes over time
Nodules <10 mm: view on thin slices (≤1.5 mm, ideally 1 mm) with high-spatial frequency (sharp) algorithm to avoid partial volume averaging
Volumetric software: use same software for initial and all follow-up studies

Size & Description

3–10 mm Express as average of short-axis and long-axis diameters (same slice)
<3 mm Do not measure — describe as micronodules
>10 mm Describe in both short- and long-axis measurements
Round all measurements to the nearest whole millimetre
Part-solid: report maximal diameter of solid component if >3 mm
Part-solid morphology cannot be reliably discerned when <6 mm
Multiple nodules: measure only the largest or morphologically most suspicious
Dominant nodule = most suspicious lesion, not necessarily the largest
Significant growth = increase in nodule dimension by ≥2 mm
Volume doubling time can be used as an ancillary feature to characterise nodule behaviour
Perifissural nodules with characteristic morphology (triangular/oval axially, flat/lentiform in sagittal/coronal) do not require follow-up even if >6 mm

⚠ Guideline Exclusions — These Patients Are Out of Scope ▾

Age ≤35 Overall low risk for pulmonary malignancy — nodules more likely infectious than cancer. Individualise management.
Known malignancy Incidentally detected nodule is more likely cancer-related than in the general population. Manage accordingly.
Immunocompromised Higher risk for opportunistic pulmonary infections — guideline thresholds do not apply directly.
Lung cancer screening Active screening patients (typically current/former smokers) should be reported per Lung-RADS, not Fleischner.

🔍 Specific Scenarios & Technical Caveats ▾

Thick-Slice Scans (>2 mm slice thickness)

The 2017 guideline does not directly address this scenario
For nodules ≥6 mm: some authors recommend a complete thin-slice CT chest as early as possible to determine accurate management

Incomplete CT Scans (e.g. abdomen or neck scans)

≤8 mm Nodules can follow the standard Fleischner guideline
>8 mm Or those with very suspicious features — complete chest CT as early as possible

Risk Factor Impact

—

References & Original Research ↕ Hover to expand

MacMahon H, et al. Guidelines for Management of Incidental Pulmonary Nodules Detected on CT Images. Radiology 2017;284:228–243. View ↗

Bankier AA, et al. Recommendations for Measuring Pulmonary Nodules at CT. Radiology 2017;285:584–600. View ↗

American College of Radiology. Lung-RADS Assessment Categories v2022. Visit ↗