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Benign nodules include nodules with complete, central, popcorn, concentric rings calcifications and fat containing nodules.

The modifier “S” may be added to Lung-RADS categories 0-4 for clinically significant or potentially clinically significant findings unrelated to lung cancer.

Probability of malignancy for each category. Category 1. < 1%. Category 2. < 1%. Category 3. 1-2%. Category 4A. 5-15%. Category 4B and 4X. > 15%.

Estimated prevalence among screening population. Category 0. 1%. Category 1. 39%. Category 2. 45%. Category 3. 9%. Category 4A. 4%. Category 4B and 4X. 3%. Modifier “S”. 10%.

Nodule size: nodules should be measured on lung windows. To calculate nodule mean diameter, measure both the long and short axis to one decimal point in mm, and report mean nodule diameter to one decimal point. The long and short axis measurements may be in any plane to reflect the true size of the nodule. Volumes, if obtained, should be reported to the nearest whole number in mm³.

Nodule growth: An increase in mean diameter size of > 1.5 mm (> 2 mm³) within a 12-month interval.

Size Thresholds: Apply to nodules at first detection and that enlarge, reaching a higher size category. When a nodule crosses a new size threshold for other Lung-RADS categories, even if not meeting the definition of growth, the nodule should be reclassified based on size and managed accordingly.

Suspected Infectious or Inflammatory Findings:

A. Lung-RADS 0 with 1-3 month follow-up LDCT may be recommended for pulmonary findings suggesting an indeterminate infectious or inflammatory process. Such findings may include segmental or lobar consolidation, multiple new nodules (more than six), large solid nodules (≥ 8 mm) appearing in a short interval, and new nodules in certain clinical contexts (e.g. immunocompromised patient). At 1-3 month follow-up, a new Lung-RADS classification and management recommendation should be provided based on the most suspicious nodule.

B. New solid or part solid nodules with imaging features more concerning for malignancy than an infectious or inflammatory process meeting Lung-RADS 4B size criteria may be classified as such with appropriate diagnostic and/or clinical evaluation.

C. Some findings indicative of an infectious or infectious process may not warrant short-term follow-up (e.g. tree-in-bud nodules or new <3cm ground glass nodules). These nodules may be evaluated using existing size criteria with a Lung-RADS classification and management recommendation based on the most suspicious finding.