Chest · Lung cancer screening · 1.0
Lung-RADS v2022: assessment categories and management
The ACR Lung-RADS v2022 structured reporting system for low-dose CT lung cancer screening, linking nodule size and attenuation to malignancy risk and a defined management step.
Purpose
Lung-RADS standardises reporting and management of screening low-dose CT in asymptomatic high-risk adults, converting nodule size, attenuation and interval behaviour into a category with an estimated malignancy risk and a single recommended next step.
| Category | Descriptor | Representative criteria | Management |
|---|---|---|---|
| 0 | Incomplete | Part of the lungs cannot be evaluated, or prior chest CT is needed for comparison | Additional lung cancer screening CT images and/or comparison with prior chest CT examinations |
| 1 | Negative | No nodules; or nodules with benign calcification patterns, or fat-containing nodules | Continue annual screening low-dose CT in 12 months |
| 2 | Benign appearance or behaviour | Solid nodule <6 mm at baseline or new <4 mm; part-solid <6 mm total at baseline; non-solid nodule <30 mm or ≥30 mm and unchanged/slowly growing; juxtapleural nodule <10 mm with smooth margins and oval, lentiform or triangular shape; category 3 or 4 nodules stable or decreased in size at follow-up | Continue annual screening low-dose CT in 12 months |
| 3 | Probably benign | Solid nodule ≥6 to <8 mm at baseline or new 4 to <6 mm; part-solid ≥6 mm total with solid component <6 mm, or new <6 mm total; non-solid ≥30 mm at baseline or new | Six-month follow-up low-dose CT |
| 4A | Suspicious | Solid nodule ≥8 to <15 mm at baseline or new/growing 6 to <8 mm; part-solid with solid component ≥6 to <8 mm, or new/growing solid component <4 mm; atypical pulmonary cyst categories defined in v2022 | Three-month follow-up low-dose CT; PET/CT may be considered when the solid component measures ≥8 mm |
| 4B | Very suspicious | Solid nodule ≥15 mm at baseline, or new/growing ≥8 mm; part-solid with solid component ≥8 mm, or new/growing solid component ≥4 mm; more advanced atypical cyst categories | Diagnostic chest CT with or without contrast, PET/CT and/or tissue sampling, guided by malignancy probability and comorbidity |
| 4X | Category 3 or 4 nodule with additional suspicious features | Category 3 or 4 finding with imaging features or additional findings that increase suspicion of malignancy (for example spiculation, associated lymphadenopathy or metastatic disease) | Managed as category 4B: diagnostic CT, PET/CT and/or tissue sampling |
| S | Significant or potentially significant other finding | Modifier added to categories 0–4 for clinically significant non-lung-cancer findings (for example coronary calcification, aortic aneurysm, emphysema) | Managed according to the specific finding, in addition to the assigned Lung-RADS category |
How to use it
- Lung-RADS applies only to asymptomatic screening low-dose CT in an eligible high-risk population; it does not apply to diagnostic CT, to patients with known or suspected lung cancer, or to incidental nodules found outside a screening programme (where Fleischner 2017 applies).
- The category is driven by the most suspicious nodule on the examination, sized as the mean of long and short axis on a single image, recorded to one decimal place; part-solid nodules require separate reporting of total size and solid-component size.
- Version 2022 refined several elements: growth is defined as an increase of more than 1.5 mm, stable or decreasing category 3 and 4 nodules may be downgraded to category 2, juxtapleural nodule criteria were formalised, and atypical pulmonary cysts were introduced into categories 4A and 4B.
- Category assignment carries an estimated malignancy risk band (roughly <1% for categories 1–2, 1–2% for category 3, 5–15% for 4A and >15% for 4B), which is what justifies the escalating interval from 12 months to 6, then 3 months, then tissue characterisation.
- The S modifier is additive, not a substitute for the numeric category — a scan can be 2S or 4BS, and the lung cancer management step is still determined by the numeric category.
Common mistake
Applying Lung-RADS to incidental nodules on a diagnostic or staging CT instead of Fleischner 2017 criteria, and sizing a part-solid nodule by total diameter alone when the solid component determines the category.
Exam pearl
Category 4A means a 3-month CT; 4B/4X means diagnostic work-up (PET/CT and/or tissue sampling). The S modifier flags a non-lung-cancer finding and never changes the numeric category.
Viva questions
- What is Lung-RADS and to whom does it apply?
- Lung-RADS is the ACR structured reporting system for low-dose CT lung cancer screening in asymptomatic high-risk adults. It assigns a category based on nodule size, attenuation and interval behaviour, each linked to an estimated malignancy risk and a defined management step. It does not apply to diagnostic CT or to patients with known or suspected lung cancer.
- List the Lung-RADS categories.
- Categories 0 (incomplete), 1 (negative), 2 (benign appearance or behaviour), 3 (probably benign), 4A (suspicious), 4B (very suspicious) and 4X (category 3 or 4 with additional suspicious features), plus the S modifier for significant or potentially significant other findings.
- How is a nodule measured for Lung-RADS?
- As the mean of the long-axis and short-axis diameters on the same image, recorded to one decimal place. For part-solid nodules, the total size and the solid-component size are reported separately, and the solid component determines the category.
- What management follows category 3, 4A and 4B?
- Category 3 gets a 6-month low-dose CT, category 4A a 3-month low-dose CT with PET/CT considered when the solid component is at least 8 mm, and category 4B a diagnostic chest CT with or without contrast, PET/CT and/or tissue sampling.
- What does the 4X category mean?
- A category 3 or 4 nodule that carries additional imaging features or associated findings raising suspicion of malignancy, such as spiculation or associated lymphadenopathy. It is managed as category 4B.
- What did version 2022 change?
- It defined growth as an increase of more than 1.5 mm, allowed stable or decreasing category 3 and 4 nodules to be downgraded to category 2, formalised juxtapleural nodule criteria, and added atypical pulmonary cysts to categories 4A and 4B.
- What is the commonest pitfall when applying Lung-RADS?
- Using it for incidental nodules on diagnostic CT, where Fleischner 2017 criteria apply, and categorising a part-solid nodule by its total diameter instead of its solid component.