Lung-RADS Score Explained: What Each Category Means

Key Takeaways

• Lung-RADS is a 7-tier scoring system (0, 1, 2, 3, 4A, 4B, 4X) used by radiologists to standardize how lung nodules are reported on low-dose CT (LDCT) lung cancer screening exams.
• Most patients receive a Lung-RADS 1 or 2 — both of which mean "negative" with about a 1% or lower chance of cancer. Routine annual screening continues.
• Lung-RADS 3 means "probably benign" with a roughly 1–2% cancer probability and triggers a 6-month follow-up scan, not a biopsy.
• Lung-RADS 4A, 4B, and 4X are "suspicious" with cancer probabilities of 5–15%, greater than 15%, and greater than 15% respectively, and lead to PET/CT, tissue sampling, or specialist referral.
• The current version is Lung-RADS v2022, published by the American College of Radiology (ACR), and applies to all routine LDCT screening reports as of 2026.

What Lung-RADS Is and Why It Exists

Lung-RADS — short for the Lung CT Screening Reporting and Data System — is a structured scoring framework that radiologists use to report findings on low-dose CT lung cancer screening. It was first released by the ACR in 2014 and updated in 2019 and again in 2022. The current version, Lung-RADS v2022, is the standard used across U.S. screening programs in 2026.

Before Lung-RADS, two radiologists could read the same lung CT and write very different reports. One might call a small spot "suspicious," another "probably nothing." That inconsistency caused real harm: false alarms led to unnecessary biopsies, while genuine cancers were sometimes downplayed. Lung-RADS solved this by linking each category to specific size, density, and growth criteria — so the score tells you and your doctor exactly what to do next.

You can also see our concise definition of Lung-RADS in the glossary, and a more general guide to lung nodule CT scans.

Who Should Get a Lung-RADS Score?

Lung-RADS is reported only on LDCT screening scans, not on CT scans done for symptoms. According to the U.S. Preventive Services Task Force, annual LDCT lung cancer screening is recommended for adults who:

• Are between 50 and 80 years old
• Have a 20 pack-year smoking history (e.g., one pack a day for 20 years, or two packs a day for 10 years)
• Currently smoke or quit within the past 15 years

If you meet these criteria, a free or low-cost annual LDCT scan is typically covered by Medicare and most private insurance plans. The radiologist who reads your scan assigns a Lung-RADS score that drives every follow-up decision.

The Lung-RADS Categories Explained

Each Lung-RADS category answers two questions: How worrying is what we saw? and What happens next? Here is what each score means in plain language.

Lung-RADS 0 — Incomplete

A Lung-RADS 0 means the radiologist could not finish the assessment. This usually happens because:

• Part of the lung was not fully imaged
• Image quality was poor (motion, breathing artifact)
• A previous CT or PET scan is needed for comparison but not available

Cancer probability: Cannot be calculated. Follow-up: Repeat or completed imaging, or retrieval of prior scans for comparison. Lung-RADS 0 is not a finding — it is a request to finish the work.

Lung-RADS 1 — Negative

Lung-RADS 1 means no nodules were found, or the only findings were clearly benign features such as calcified granulomas (old scars from prior infections).

Cancer probability: Less than 1%. Follow-up: Continue annual LDCT screening as long as you remain eligible.

About 50–60% of screened patients receive a Lung-RADS 1 result.

Lung-RADS 2 — Benign Appearance or Behavior

Lung-RADS 2 means small nodules were seen, but their size and appearance are very low risk. Examples include:

• Solid nodules smaller than 6 mm
• Part-solid nodules where the solid component is smaller than 6 mm
• Pure ground-glass nodules smaller than 30 mm
• Stable nodules that have not grown over time

Cancer probability: Less than 1%. Follow-up: Continue annual LDCT screening.

Lung-RADS 1 and 2 are both reported as "negative" exams. Most screened patients fall into one of these two categories.

Lung-RADS 3 — Probably Benign

Lung-RADS 3 means a finding deserves a closer look in 6 months but is unlikely to be cancer. Typical findings include:

• Solid nodules between 6 and 8 mm
• Part-solid nodules where the solid component is smaller than 6 mm but the total is at least 6 mm
• New solid nodules between 4 and 6 mm

Cancer probability: 1–2%. Follow-up: A 6-month LDCT to check for growth. If the nodule is stable at 6 months, the score usually drops to Lung-RADS 2 next year.

A Lung-RADS 3 is not a reason for a biopsy, PET scan, or specialist referral on its own. It is a watch-and-wait result.

Lung-RADS 4A — Suspicious (Lower)

Lung-RADS 4A means a finding is suspicious enough to investigate further, though most still turn out to be benign. Examples:

• Solid nodules between 8 and 15 mm
• New solid nodules between 6 and 8 mm
• Part-solid nodules where the solid component is between 6 and 8 mm
• Endobronchial nodules

Cancer probability: 5–15%. Follow-up: Options include a 3-month LDCT, a PET/CT scan (typically for nodules at least 8 mm), or tissue sampling depending on the case. The choice is shared between you, your primary doctor, and a pulmonologist or thoracic specialist.

Lung-RADS 4B — Suspicious (Higher)

Lung-RADS 4B is reserved for findings with a high enough cancer probability to warrant prompt work-up. Examples:

• Solid nodules at least 15 mm
• New solid nodules at least 8 mm
• Part-solid nodules with a solid component at least 8 mm

Cancer probability: Greater than 15%. Follow-up: PET/CT, tissue sampling (biopsy), or referral to a thoracic surgeon are typical next steps. Multidisciplinary discussion is recommended.

Lung-RADS 4X — Suspicious With Additional Features

Lung-RADS 4X is a 4A or 4B nodule that also shows additional worrying features — for example, spiculated edges, enlarged lymph nodes, or pleural involvement. The "X" stands for "extra" features that increase suspicion beyond what size alone implies.

Cancer probability: Greater than 15% (often substantially higher than 4B). Follow-up: Same urgency as Lung-RADS 4B — PET/CT, tissue sampling, and specialist referral.

A Quick Comparison of Lung-RADS Scores

Modifiers You May See on Your Report

In addition to the main category, your Lung-RADS report may include modifiers:

• S — Significant non-lung finding. The radiologist saw something outside the lungs that needs attention (e.g., coronary artery calcium, an incidental finding in the thyroid or kidney).
• C — Prior lung cancer. Indicates the patient has a known history of lung cancer.

These modifiers do not change the lung cancer probability of the main score; they flag additional information for your doctor.

What Happens If Your Score Is 3 or Higher

Receiving a Lung-RADS 3 or 4 can be unsettling. Some context that may help:

• Most Lung-RADS 3 and 4A nodules are not cancer. A score of 3 has only a 1–2% cancer rate, and 4A is 5–15%. Most patients in these categories end up with benign results after follow-up.
• The system is intentionally cautious. ACR designed Lung-RADS to catch early cancers while minimizing biopsies. The 6-month or 3-month re-scan is a low-risk way to see whether a nodule grows.
• Insurance issues can arise. Diagnostic CT, PET/CT, and biopsies are billed differently from screening LDCT. If your follow-up is denied, our guide on prior authorization for medical imaging explains how appeals work.
• Anxiety while waiting is normal. "Scanxiety" between the screening and follow-up is well documented. See our guide on managing imaging results anxiety.

For nodules found outside structured screening — for example, a nodule discovered on a routine chest CT — the Fleischner Society criteria are typically used instead of Lung-RADS.

Frequently Asked Questions

Is Lung-RADS the same as a cancer diagnosis?

No. Lung-RADS is a probability category based on imaging features, not a diagnosis. Even Lung-RADS 4B has a cancer probability of greater than 15%, which means most 4B nodules also turn out to be benign. A diagnosis requires tissue sampling (biopsy) or surgical removal followed by a pathologist's review.

Why did my Lung-RADS category change between two annual scans?

Lung-RADS reflects the most recent imaging. A nodule that grew, became more solid, or developed new features will move to a higher category. A nodule that has remained stable across scans usually moves to a lower category — often to Lung-RADS 2 — because stability over time is itself reassuring. According to ACR, the system is designed to use change over time as a key signal.

Does a Lung-RADS 4 score always mean a biopsy?

No. Lung-RADS 4A often leads to a 3-month follow-up CT or a PET/CT before any biopsy is considered. Lung-RADS 4B and 4X usually trigger PET/CT or tissue sampling, but the exact next step depends on the nodule's size, location, your overall health, and a multidisciplinary discussion. Some 4B nodules in high-risk locations may be removed surgically without a separate biopsy.

Will my insurance cover the follow-up scan after a Lung-RADS 3 or 4?

Routine annual screening LDCT is widely covered when you meet eligibility criteria. Follow-up scans (3-month or 6-month CT, PET/CT) are usually billed as diagnostic imaging, which can require prior authorization and a copay. Check coverage before scheduling. The same applies if you receive a recommendation for follow-up at any tier.

Can I be screened if I quit smoking more than 15 years ago?

Under current USPSTF guidance, screening eligibility ends 15 years after quitting. Some specialists make exceptions for patients with strong family histories or other risk factors, but insurance coverage typically follows the USPSTF rule. Talk to your primary care doctor about your individual risk.

Related Articles

• Lung nodule on a CT scan: what it means and what to do next
• How to read a chest X-ray report
• Prior authorization for medical imaging — how to handle denials
• Scanxiety: managing imaging results anxiety

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Disclaimer: This article is for educational purposes only and does not constitute medical advice. Always consult with a qualified healthcare professional for diagnosis and treatment decisions.