Lung-RADS

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Lung-RADS (or lung imaging reporting and data system) is a classification proposed to aid with findings in low-dose CT screening exams for lung cancer. The goal of the classification system is to standardize follow-up and management decisions. The system is similar to the Fleischner criteria but designed for the subset of patients intended for low-dose screening studies.

Classification system

Category 0 (incomplete)
  • prior CT studies were performed, but are not available for comparison
  • lungs are incompletely imaged
Category 1 (negative, <1% chance of malignancy)
  • no lung nodules
  • lung nodule(s) with specific findings favoring benign nodule(s)
    • complete calcification
    • central calcification
    • popcorn calcification
    • calcification in concentric rings
    • fat-containing nodules
Category 2 (benign appearance, <1% chance of malignancy)
  • solid nodule(s)
    • <6 mm at baseline
    • new nodule <4 mm
  • subsolid nodule(s)
    • <6 mm on baseline screening
  • ground glass nodule(s)
    • <30 mm (Version 1.1 change previously 20 mm)
    • ≥30 mm and unchanged or slowly growing (Version 1.1 change previously 20 mm)
  • category 3 or 4 nodules that are unchanged for ≥3 months
Category 3 (probably benign, 1-2% chance of malignancy)
  • solid nodule(s)
    • ≥6 mm to <8 mm at baseline
    • new nodule 4 mm to <6 mm
  • subsolid nodule(s)
    • ≥6 mm total diameter with solid component <6 mm
    • new <6 mm total diameter
  • ground glass nodule(s)
    • ≥30 mm on baseline CT or new (Version 1.1 change previously 20 mm)
Category 4A ( Probably suspicious, 5-15% chance of malignancy) (Version 1.1 change previously suspicious)
  • solid nodule(s)
    • ≥8 mm to <15 mm at baseline
    • growing nodule(s) <8 mm
    • new nodule 6 mm to <8 mm
  • subsolid nodule(s)
    • ≥6 mm total diameter with solid component ≥6 mm to <8 mm
    • new or growing <4 mm solid component
  • endobronchial nodule
Category 4B (suspicious, >15% chance of malignancy)
  • solid nodule(s)
    • ≥ 15 mm at baseline
    • new or growing, and ≥8 mm
  • subsolid nodule(s)
    • solid component ≥8 mm
    • new or growing ≥4 mm solid component
  • For new large nodules that develop on an annual repeat screening CT, a 1 month LDCT may be recommended to address potentially infectious or inflammatory conditions. (Version 1.1 addition)
Category 4X (suspicious, >15% chance of malignancy)
  • category 3 or 4 nodules with additional features or imaging findings that increase the suspicion of malignancy
  • includes:
    • spiculation
    • ground glass nodule(s) that double in size in 1 year
    • enlarged regional lymph nodes
  • For new large nodules that develop on an annual repeat screening CT, a 1 month LDCT may be recommended to address potentially infectious or inflammatory conditions. (Version 1.1 addition)
Modified categories
  • [X]S (e.g. "3S") if there is a clinically significant or potentially significant non-lung cancer finding
  • (Version 1.1 REMOVAL): [X]C (e.g. "3C") for a patient with a prior diagnosis of lung cancer who returns to screening

Recommended follow-up

Category 0:

  • comparison with prior studies before assignment of Lung-RADS classification

Category 1: 

  • continue annual screening with LDCT

Category 2: 

  • continue annual screening with LDCT

Category 3: 

  • 6-month follow-up with LDCT

Category 4A: 

  • 3-month follow-up with LDCT
  • PET/CT may be used if there is a ≥8 mm solid component

Category 4B and 4X: 

  • chest CT with or without contrast, as appropriate
  • PET-CT and/or tissue sampling depending on the probability of malignancy and comorbidities (PET-CT if solid component ≥8 mm)
  • For new large nodules that develop on an annual repeat screening CT, a 1 month LDCT may be recommended to address potentially infectious or inflammatory conditions. (Version 1.1 addition)

Practical points

  • nodule measurement should be in lung windows
  • To calculate nodule mean diameter, measure both the long and short axis to one decimal point, and report mean nodule diameter to one decimal point. [previously recommended rounding to nearest whole number version 1.0.]
  • only a single measurement is necessary for round nodules
  • "growth" is an increase in size of ≥1.5 mm
  • assignment of a Lung-RADS status is based on the most suspicious nodule
  • category 4B management is based on multiple factors including overall patient status and patient preference
  • Solid nodules with smooth margins, an oval, lentiform or triangular shape, and maximum diameter less than 10 mm (perifissural nodules) should be classified as category 2. (Version 1.1 addition)

See also