Lung-RADS is a standardized reporting system that assigns a number from 0 to 4 to findings on a low-dose CT lung cancer screening scan. The 2022 update refined several categories, added a new 4A designation for some infectious or inflammatory findings, and clarified how to handle nodules that change over time. The number is not a diagnosis. It is a risk signal that tells your doctor when the next scan should happen and whether more testing is needed now.
What Is Lung-RADS and Why Does the Score Matter?
Lung-RADS stands for Lung Imaging Reporting and Data System. It was developed by the American College of Radiology to bring consistency to how radiologists report low-dose CT screening results. Before it existed, two radiologists could look at the same nodule and describe it in completely different ways. One might say “follow up in three months.” Another might say “recommend biopsy.” Neither would be wrong, but neither would be standardized.
The system works much like BI-RADS for mammography. A radiologist evaluates the size, density, and growth pattern of anything found in the lungs, then assigns a category. That category comes with a recommended next step. The goal is to catch lung cancers early while avoiding unnecessary procedures on findings that are almost certainly benign.
Lung-RADS is specifically designed for screening. It applies to people without symptoms who qualify for annual low-dose CT screening. It does not apply to CT scans done because someone has a cough, chest pain, or other concerning symptoms. Those scans follow a different diagnostic pathway entirely.
What Do the Lung-RADS Categories 0 Through 4 Mean?
Each category reflects a different level of suspicion and comes with a specific recommended action.
- Category 0: The scan was incomplete or a previous scan is needed for comparison. This is not a finding — it means the radiologist needs more information before assigning a final score.
- Category 1: No nodules and no lung abnormalities. Continue annual screening.
- Category 2: A nodule or finding with a very low likelihood of becoming cancer. This includes benign patterns like certain calcifications or stable nodules under a specific size threshold. Continue annual screening.
- Category 3: Probably benign, but short-interval follow-up is recommended — typically in about six months. The concern is low but not zero.
- Category 4A: Suspicious enough to warrant additional testing or a shorter follow-up interval, usually around three months. In the 2022 update, some infectious or inflammatory findings were added to this category to reduce unnecessary workups.
- Category 4B: More suspicious. Follow-up imaging or tissue sampling is recommended, often within one to three months depending on the specific finding.
- Category 4X: Highly suspicious for cancer. Tissue sampling or further diagnostic evaluation is recommended.
The jump from 3 to 4 is where clinical decisions get more serious. A category 3 nodule is watched. A category 4 nodule usually gets acted on.
How Does Nodule Size and Type Affect the Score?
Size matters, but it is not the only factor. Density and appearance carry real weight.
Solid nodules — those that completely obscure the lung tissue behind them on CT — are scored primarily by their average diameter. The larger the nodule, the higher the category. The 2022 update kept the same size thresholds for solid nodules that were in the original 2014 version.
Part-solid nodules have both a solid component and a ground-glass component. These are scored based on the solid portion, not the total size. A part-solid nodule with a small solid component may score lower than a solid nodule of the same overall diameter. This distinction matters because the solid component is what carries the higher risk.
Ground-glass nodules appear hazy and do not obscure underlying structures. They are often slower-growing and may be followed with longer intervals. Some ground-glass nodules resolve on their own.
Atypical findings like a thicker airway wall or a fluid collection around the lung may also influence the score. The 2022 update added specific guidance for some of these presentations, particularly when they are likely infectious or inflammatory.
What Changed in the 2022 Update?
The 2022 version of Lung-RADS made several adjustments based on accumulated screening data. The most discussed change was the addition of certain infectious or inflammatory findings to category 4A. Before this update, some of these findings might have been scored higher or handled inconsistently. The revision aimed to reduce unnecessary biopsies for things that were likely not cancer.
The update also refined follow-up timing for some categories and clarified how to handle nodules that appear new or grow between scans. Growth remains one of the strongest signals of potential malignancy. A nodule that grows is scored higher than a stable nodule of the same size.
These changes are not dramatic. Most of the core structure — the categories, the size thresholds, the general approach — remained intact. The update was a refinement, not an overhaul.
How Should You Use Your Lung-RADS Score?
Your score is a tool for your doctor. It tells them what to do next. It does not tell you whether you have cancer.
A category 1 or 2 result is reassuring. It means the scan found nothing that requires immediate action beyond continuing your annual screening. That is the most common outcome.
A category 3 result means a follow-up scan in about six months. This is not an emergency. It is a cautious approach to something that is probably benign but worth watching.
A category 4 result means your doctor will likely recommend additional imaging or a procedure to get a tissue sample. This does not mean you have cancer. It means the finding is suspicious enough that waiting a full year is not appropriate.
Ask your doctor two questions: What specific finding led to this score, and what is the recommended next step? Those two pieces of information matter more than the number itself.
What Lung-RADS Does Not Tell You
Lung-RADS is a screening tool. It is not a diagnostic test. A high score does not confirm cancer. A low score does not rule it out.
The system also does not apply to people who have symptoms. If you have a persistent cough, coughing up blood, unexplained weight loss, or chest pain, you need a diagnostic evaluation — not a screening score. Lung-RADS was not designed for that situation.
It also does not apply to CT scans done for other reasons, such as evaluating pneumonia or monitoring a known condition. Those scans follow different reporting standards.
Finally, Lung-RADS does not replace clinical judgment. A radiologist assigns the score. Your doctor interprets it in the context of your history, your risk factors, and your preferences. The score is one piece of a larger picture.
Frequently Asked Questions
What does Lung-RADS category 4A mean?
Category 4A means the finding is suspicious enough to warrant additional testing or a shorter follow-up interval, usually around three months. In the 2022 update, some infectious or inflammatory findings were also placed in this category to reduce unnecessary procedures.
Is Lung-RADS 4 always cancer?
No. A category 4 score means the finding is suspicious and needs further evaluation, but many category 4 findings turn out to be benign. The score indicates that waiting a full year for the next scan is not appropriate.
How often should I get screened if my Lung-RADS score is 1 or 2?
Categories 1 and 2 both recommend continuing annual low-dose CT screening. No additional follow-up beyond your regular yearly scan is needed for either category.
Does Lung-RADS apply to CT scans done for symptoms?
No. Lung-RADS is designed specifically for lung cancer screening in people without symptoms. If you have symptoms like a persistent cough or coughing up blood, your doctor will use a different diagnostic approach.
