Caveats for using the Fleishner guidelines calculator for incidental pulmonary nodules:

• Applicable for patients ≥35 years old with incidental pulmonary nodules on CT imaging.
• Not to be used for
  • Lung cancer screening
  • For patients with known primary cancer
  • Immunocompromised patients.
• Management depends on the most suspicious lung nodule.
• IN ADULTS, all CT scans of the thorax should be reconstructed and archived with contiguous thin sections (≤1.5 mm, typically 1.0 mm) to accurately characterize and measure small pulmonary nodules. Multiplanar reformats in the sagittal and coronal planes are also recommended.
• Follow-up CT studies should be performed with a low dose protocol.
• For smaller nodules, dimensions are average of long and short axes, rounded to the nearest millimeter. Thus the size threshold (<6 mm) corresponds to a rounded measurement of 5 mm or less as per these guidelines.
• For nodules more than 10mm both long and short axes dimensions are documented.
• Volume thresholds of 100 and 250 mm3 are used for volumetry instead of the 6- and 8-mm thresholds used for linear measurements.
• Prior imaging studies should always be viewed to assess stability. Comparison between the earliest available study and the most recent study should be performed.
• All attenuation measurements for nodules should be made on the thinnest available soft-tissue window images.
• Risk Factors for Malignancy
  • Nodule Size and Morphology: Larger nodules and spiculated margins are worrisome.
  • Nodule Location:
    • Lung cancer - Upper lobes.
    • Adenocarcinoma and Mets- Peripheral portions
    • Squamous cancers - Near hila
    • Perifissural solid nodules are usually benign intrapulmonary lymph nodes.
  • Nodule Multiplicity: Multiplicity is associated with a lower risk of malignancy especially > 5.
  • Nodule Growth Rate: Volume doubling time for cancers are in the range of 100–400-day range and correspond to an increase in diameter by 26%.
  • Emphysema and Fibrosis: Increased risk.
  • Age, Sex, Race, and Family History
  • Tobacco and Other Inhaled Carcinogens
• Follow-up CT is NOT recommended when small nodules have a perifissural or other juxtapleural location and a morphology consistent with an intrapulmonary lymph node, even if the average dimension exceeds 6 mm.
• Recommendations for nodules detected on incomplete CT chest studies, for eg. Nodules at lung bases covered on CT abdomen:
  • Most small nodules (<6 mm) - No further investigation
  • Intermediate-size nodules (6–8-mm) nodules- Follow-up CT of the complete chest after an appropriate interval (3–12 months depending on clinical risk) to confirm stability and to evaluate additional findings.
  • Large or very suspicious nodule -  Complete dedicated CT thorax examination for further evaluation.

Fleischner Society 2017 Guidelines for Management of Incidentally Detected Pulmonary Nodules in Adults

Reference: Guidelines for Management of Incidental Pulmonary Nodules Detected on CT Images: From the Fleischner Society 2017 Heber MacMahon et.al. Radiology 2017 284:1, 228-243. Read the complete article here: https://pubs.rsna.org/doi/10.1148/radiol.2017161659