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 many possible causes — infection, inflammation, scarring, and sometimes early tumors. A GGO is a finding to follow up, not a diagnosis. Radiologists and your doctor decide on next steps, often a repeat scan after a period of time.
A ground-glass opacity is a hazy area on a lung CT — a description, not a diagnosis.
Common causes include infection and inflammation; most GGOs are not cancer.
Follow-up often means a repeat scan later to see whether it changes.
Only your care team, with the full picture, can say what yours means.
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The full explanation.
Where you'll see this phrase
In a CT scan report of the chest: "ground-glass opacity," "GGO," or "ground-glass nodule." It may be described as focal (one spot) or diffuse (spread out), and as pure or part-solid.
What it means in plain language
On a CT, dense things (like bone) look white and air looks black. A ground-glass opacity is an area that's hazier than normal lung but not solid white — you can still see the lung's fine markings through it, like looking through frosted glass.
Why it may matter — and often doesn't
GGO is a description of an appearance, and many different things cause it:
- Infection (including pneumonia)
- Inflammation or irritation
- Old scarring
- Fluid
- Sometimes early tumors or precancerous change
Because the list is broad and most causes aren't cancer, doctors usually follow a GGO rather than jump to conclusions. How it behaves over time is a key clue.
What it does not mean
- A GGO is not a cancer diagnosis.
- A single scan usually can't settle the cause — which is why comparison over time is so useful.
What context is still needed
The size, shape, whether it's solid or part-solid, your history, and any symptoms all shape what a GGO means. Your doctor and radiologist put those together to decide on follow-up.
Words to know
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Common questions
▸Does a ground-glass opacity mean lung cancer?
Not usually. GGOs have many causes, and infections or inflammation are common. Some persistent GGOs can represent early tumors, which is why doctors track them over time rather than ignoring or panicking about them.
▸Why does my doctor want another scan later?
Comparing scans over time shows whether a GGO resolves, stays the same, or grows. That pattern is one of the most useful clues to its cause and guides whether anything more is needed.
Questions to ask your doctor
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Your next step
Plain-language definitions for the words on your report.
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