Ground-glass opacity on a chest CT: patchy haze or a single spot

The words next to it

Words you may see beside ground-glass opacity on a report, and what each one changes.

Patchy, diffuse, bilateral

Patchy is scattered areas, diffuse is widespread, bilateral is both lungs. These describe the haze kind, judged by how it changes over time rather than by size.

Ground-glass nodule (GGN), focal, nodular

One rounded hazy spot, usually given a size in millimeters, and the kind with set follow-up rules.

Pure vs part-solid

Pure is hazy all the way through. Part-solid also has a solid part, which the report may measure on its own because the plan turns on its size.

Peripheral, subpleural, lower lobe

At the outer edge of the lung, just under its lining, low down. Haze at the edges of both lower lungs is the typical pattern in acute COVID-19, though not the only cause.

Resolved, transient vs persistent

Resolved or transient means it was gone on a later scan. Persistent means it's still there.

Multiple ground-glass nodules

Several hazy spots. The usual first step is a repeat CT at 3 to 6 months, and if they're stable, scans at 2 and 4 years may be considered.

When the haze is patchy

With patchy haze, timing is a key clue. Acute ground glass lasts days or weeks. Chronic ground glass can look much the same for many weeks, even years.

One scan can't show how long the haze will last, so an impression like the one above suggests a follow-up CT "to confirm resolution." Haze that has cleared by then fits an acute cause.

When it's a single spot, and why it's watched for years

A single pure ground-glass nodule under 6 mm gets no routine follow-up in the Fleischner Society's 2017 table. At 6 mm or more, a CT at 6 to 12 months checks that it's still there, then one every 2 years until 5 years. A part-solid nodule of 6 mm or more is checked sooner, at 3 to 6 months, then yearly for 5 years if its solid part stays under 6 mm.

Many of these spots go away on their own. In one study, 27% of suspicious ground-glass and part-solid nodules turned out to be transient, from inflammation.

A spot that doesn't go away is often an early lung cancer or a precancer, and that's the question the follow-up answers. But these change slowly. A pure one takes roughly 600 to 900 days to double in volume, a part-solid one 300 to 450. About 20% of pure and 40% of part-solid spots slowly grow or get more solid, and the rest stay unchanged for years. So a spot that looks the same next time hasn't been ignored.

If you're in cancer care, or this was a lung cancer screening scan, that table isn't your plan. It's written for adults 35 or older whose spot turned up on a CT done for another reason, without a known cancer elsewhere. On a staging or surveillance scan, the team treating the cancer sets the follow-up.

Questions to ask the doctor

• Is mine patchy haze, a single ground-glass nodule, or both?
• If it's a nodule, what size is it, and is any part of it solid?
• Does my cancer history, or this being a screening scan, change how often it gets checked?
• When is my next CT, and what change on it would lead to more tests?

Often on the same report

• Consolidation

  Part of the lung that should hold air is filled with something else, like pus, fluid, blood, or cells, so it looks solid and white on the scan. Causes include pneumonia, fluid from heart failure, bleeding, and tumors.

• Pulmonary nodule

  A small spot in the lung, under 3 cm across. They're common, found in up to half of adults who have a chest X-ray or CT. Most small ones aren't cancer and come from infection, scars, or lymph nodes, but some can be early lung cancer.

• Opacity

  An area on the image that looks whiter or denser than expected, often in the lungs. It describes how something looks, not what it is, and it can come from fluid, infection, or a mass, among other things.

• Airspace disease

  Parts of the lung that normally hold air are filled with something else, such as fluid, pus, blood, or cells, so they look whiter on the image. Pneumonia and fluid in the lungs are common causes, and other findings and the person's history help narrow it down.

• Mosaic attenuation

  On the CT, the lungs look like a patchwork of darker and lighter areas. The pattern alone doesn't point to one cause. It can come from small-airway disease that traps air, blood vessel problems such as old clots, or patchy fluid, bleeding, or infection.

• Resolved

  Something seen on an earlier scan has cleared up or is no longer seen. Follow-up scans are sometimes done just to confirm this.

Questions people ask

What is ground-glass in CT?

It's lung that looks grayer and hazier than normal on a CT scan, like frosted glass, with the airways and blood vessels still showing through. "Opacity" means the area blocks more of the X-ray beam than healthy, air-filled lung does.

What causes diffuse opacity in the lungs?

Ground-glass haze comes from fluid, blood or cells partly filling the tiny air sacs, or from thickened air-sac walls and lung tissue. Many conditions do that, and whether the haze lands in patches, in one area or across both lungs depends on the cause.

Does ground-glass opacity mean cancer?

Not on its own. Focal scarring, inflammation and bleeding all cause it too. Early lung cancer comes into the question mainly with a single rounded spot that doesn't go away.

How do you fix ground glass opacities?

There's no treatment for the haze as such; what happens depends on its cause. For a ground-glass spot that changes on a follow-up scan, doctors may add blood tests, a PET/CT scan, or a needle biopsy of the lung.

Other phrases explained: Pulmonary nodule · Aortic atherosclerosis · Schmorl's node · Bone marrow edema