Lung-RADS — What It Means on Your Imaging Report
Quick Answer
Lung-RADS is a scoring system (1–4) used to classify findings on low-dose CT lung cancer screening — the category tells your doctor what follow-up is needed.
What Is Lung-RADS?
Lung-RADS stands for Lung CT Screening Reporting and Data System. It was developed by the American College of Radiology (ACR) to standardize how radiologists report and manage findings from low-dose CT (LDCT) lung cancer screening exams. Just as BI-RADS provides a consistent framework for breast imaging, Lung-RADS gives every radiologist a common language for lung screening results.
Lung cancer screening with low-dose CT is recommended for people at high risk — typically adults aged 50 to 80 with a significant smoking history. The National Lung Screening Trial showed that LDCT screening reduced lung cancer deaths by 20%. However, screening also finds many small nodules that are not cancer. Lung-RADS helps doctors distinguish findings needing immediate attention from those requiring only routine follow-up.
An important distinction: Lung-RADS applies specifically to lung cancer screening CT scans. If a nodule is found incidentally on a CT done for another reason, the Fleischner Criteria are used instead. The two systems have different thresholds because the patient populations and clinical contexts differ.
Categories / Classification
| Lung-RADS | Assessment | What It Means | Recommended Action |
|---|---|---|---|
| 1 | Negative | No lung nodules, or nodules with definitely benign features (such as complete calcification) | Continue annual LDCT screening |
| 2 | Benign Appearance | Small nodules that are very likely benign — solid nodules smaller than 6 mm, or ground-glass nodules smaller than 30 mm | Continue annual LDCT screening |
| 3 | Probably Benign | Nodules that are probably benign but large enough to warrant a closer look — solid nodules 6–8 mm, new solid nodules under 4 mm, or ground-glass nodules 30 mm or larger | Follow-up LDCT in 6 months |
| 4A | Suspicious | Findings with features that raise concern — solid nodules 8–15 mm, growing nodules, or part-solid nodules with a solid component under 6 mm | Follow-up LDCT in 3 months, or PET/CT may be recommended |
| 4B | Very Suspicious | Findings with a high probability of being malignant — solid nodules 15 mm or larger, new or growing part-solid nodules with a solid component 8 mm or larger | Chest CT with or without contrast, PET/CT, and/or tissue sampling (biopsy) |
| 0 | Incomplete | The scan is incomplete or cannot be fully evaluated — prior CT scans may be needed for comparison, or additional imaging is required | Additional imaging or prior exams needed for comparison |
| S | Other Significant Findings | Clinically significant finding not related to lung cancer (such as an aortic aneurysm or significant coronary calcification) | Follow-up as clinically appropriate based on the specific finding |
When You Might See This on Your Report
You will see a Lung-RADS category if you undergo a low-dose CT lung cancer screening exam:
- Annual lung cancer screening — Adults aged 50–80 with a 20-pack-year or greater smoking history qualify under current USPSTF guidelines.
- Follow-up screening — Returning for scheduled follow-up after a prior Lung-RADS 2 or 3 result.
- Baseline screening — Your first screening CT serves as a baseline for future comparisons.
The Lung-RADS category appears in the Impression or Assessment section of your report, alongside descriptions of any nodules found.
Should I Be Worried?
For the majority of people who undergo lung cancer screening, the results are reassuring. Studies show that approximately 90% of screening results fall into Lung-RADS categories 1 or 2, meaning no lung nodules or only small nodules with benign characteristics that require nothing more than continued annual screening.
Here is what each category generally means for you:
Lung-RADS 1 and 2 — Normal or expected results. Small nodules in this range are overwhelmingly benign. Continue annual screening as scheduled.
Lung-RADS 3 — Probably benign, with an estimated 1–2% probability of malignancy. A 6-month follow-up CT confirms stability, and the vast majority are reclassified as Lung-RADS 2 on follow-up.
Lung-RADS 4A — Needs closer evaluation with a 3-month follow-up CT or PET/CT. Estimated malignancy probability is approximately 5–15%, but the majority still turn out benign.
Lung-RADS 4B — The most concerning category, typically leading to additional imaging and possible biopsy. Prompt follow-up is important.
Lung-RADS 0 and S — Category 0 means more information is needed. Category S means the radiologist noticed something outside the lungs that may need separate attention.
What Should I Do Next?
- Check your Lung-RADS category in the Impression or Assessment section of your report. This single number tells you and your doctor the recommended next step.
- Follow the recommended timeline. If your result is Lung-RADS 1 or 2, schedule your next annual screening. If it is 3 or higher, schedule the recommended follow-up on time — the specific interval matters.
- Talk to your doctor about your result. Your doctor can explain the finding in the context of your personal risk factors, including your smoking history, family history, and overall health. For tips on this conversation, see our guide on how to discuss imaging results with your doctor.
- Bring prior imaging to your appointments. Comparing current and prior scans is one of the most important factors in evaluating lung nodules. If you have had previous chest CTs, make sure they are available to your radiologist.
- Do not skip your annual screening. Even if your current result is Lung-RADS 1, the purpose of screening is ongoing monitoring. Lung cancer found early through screening has a significantly higher survival rate than lung cancer found after symptoms develop. Staying on schedule is one of the most important things you can do for your health.