The short answer
A "ground-glass opacity" (GGO) is a hazy, gray area on a lung CT scan where you can still see the lung markings through it. It has several possible causes, some not cancer and some cancer. A GGO is a finding to follow up, not a diagnosis. Radiologists and your doctor decide on next steps, which often include repeat scans over time.
A ground-glass opacity is a hazy area on a lung CT — a description, not a diagnosis.
Causes include benign conditions and cancer, so a GGO needs follow-up.
Follow-up often means repeat scans to see whether it changes.
Only your care team, with the full picture, can say what yours means.
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This page is for people whose lung CT report mentions ground-glass opacity. It explains what the term means, how risk differs by type, and why these findings are often watched over time.
What ground-glass opacity looks like
Ground-glass opacity, often shortened to GGO, describes a hazy area on a lung CT scan. The lung tissue looks cloudy instead of clear. You can still see the blood vessels and airways through it, the way you can see shapes through frosted glass. This is different from a solid nodule, where the area is completely opaque and blocks the view of what is behind it.
Two kinds: pure and part-solid
Radiologists split these findings into two groups, because they carry different risk.
A pure ground-glass nodule is hazy all the way through. It has no solid component anywhere inside it. In one early lung cancer screening study (ELCAP), about 18% of pure ground-glass nodules turned out to be malignant (cancer).
A part-solid nodule has a hazy portion and a denser, solid portion together. These carry meaningfully higher risk. In that same study, about 63% of part-solid nodules were malignant.
How these nodules are followed
Persistent ground-glass nodules typically progress slowly. Follow-up depends on the size of the nodule and whether it has a solid part. The Fleischner Society guidance, as summarized in a National Library of Medicine (PMC) review, includes repeat CT scans over several years for many of them. For part-solid nodules with a larger solid part, it recommends biopsy or surgery if the nodule persists. Follow-up schedules have been updated over time, so ask your care team for your own plan and do not skip scans.
What ground-glass opacity does not tell you
A ground-glass appearance by itself does not tell you what caused it. It could be cancer, or a benign cause such as focal scarring or bleeding in the lung tissue. That is why a repeat scan is often used to see whether it changes.
Why persistence matters
A ground-glass finding that is still there on later scans gets closer attention, and for some part-solid nodules that persist, biopsy or surgery is recommended. Tell your care team about any new symptoms, and get emergency help (911) for severe trouble breathing.
What to ask your team
- Is my finding pure ground-glass, or does it have a solid component?
- Has this been seen on a prior scan, or is it new?
- What is the recommended follow-up schedule, and how long will I need monitoring?
- What changes on a future scan would prompt a biopsy?
Sources
Common questions
Does a ground-glass opacity mean lung cancer?
Not always, but it can. GGOs have several causes, including benign ones such as focal scarring or bleeding. Some are cancer, which is why doctors track them over time. Ask your care team what yours most likely is.
Why does my doctor want another scan later?
Comparing scans over time shows whether a GGO changes. Persistent ones are followed more closely, and some need a biopsy or surgery. Your care team sets the schedule.
Questions to ask your doctor
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Last updated: 2026-10-16Next planned review: 2027-07-12
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Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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