A lung nodule is a small irregular growth in your lungs that’s smaller than 30 millimeters (mm) (1.2 inches) in diameter. They’re very common and estimated to occur in anywhere from 2% to 24% of people in the general population. Doctors often discover them on chest X-rays or computed tomography (CT) scans for unrelated conditions.

Most lung nodules aren’t cancerous. Noncancerous causes include:

Nodule size and growth rate are the two main factors doctors use to determine the risk of a nodule being cancerous, along with shape and pattern of calcification.

Small nodules often don’t require treatment. Doctors may recommend follow-ups or surgery for large nodules, especially if you’re somebody at a high risk of developing lung cancer.

Read on to learn more about how lung nodule management varies by size.

lung nodule on an X-ray, lung nodule size chartShare on Pinterest
A lung nodule detected in a chest X-ray. Image courtesy of Lange123/CC BY-SA 3.0 from Wikimedia Commons.

Most nodules don’t cause symptoms and don’t require treatment. Larger nodules are more likely to be cancerous and require surgical removal.

The most common guidelines that doctors follow to determine how to treat a nodule are called the Fleischner Society guidelines. The Fleischner Society is an international medical group dedicated to the diagnosis and treatment of chest disease.

Their guidelines advise doctors on how to manage lung nodules based on factors such as:

  • nodule size
  • how quickly the nodule grows
  • tissue composition of the nodule

Their guidelines don’t apply to people younger than 35 or with a history of cancer or immunosuppression.

What’s considered a small lung nodule?

Lung nodules are usually considered small if they’re under 10 mm in diameter. Nodules under 3 mm are considered micronodules.

Here’s a look at the risk of small nodules becoming cancerous.

Diameter sizeRisk of being cancerous
1–2 mmThese nodules are routinely found and have a very small risk of being cancerous.
Under 6 mmStudies report anywhere from a 0%–1% chance of being cancerous.
6–8 mmThese nodules have about a 0.5%–2.0% chance of being cancerous.
More than 8 mmThere’s about a 9.7% chance of being cancerous for nodules larger than 8 mm.
More than 10 mmThese have about a 15.2% chance of being cancerous. Most tumors smaller than 10 mm are only visible on a CT scan and not on a chest X-ray.

What’s considered a large lung nodule?

Large nodules are usually considered to be greater than 10 mm in diameter. The risk of them being cancerous increases as they become bigger. By definition, a nodule is smaller than 30 mm.

Diameter sizeRisk of being cancerous
Larger than 10 mmThe chances of nodules larger than 10 mm being cancerous are about 15.2%.
Larger than 30 mmTumors larger than 30 mm are considered lung masses and are usually assumed to be cancerous.

If you’re at low risk of developing lung cancer, a doctor will likely tell you that you don’t need regular follow-ups for nodules under 6 mm. Younger age and not smoking are associated with low risk. A doctor may want to follow up with a CT scan if you’re at high risk.

A doctor will likely want to monitor nodules that are between 6 and 8 mm with one or more CT scans to see if they grow over time.

For nodules larger than 8 mm, a doctor will likely want to follow up with some combination of:

The next step depends on:

  • how large the nodule is
  • how many nodules a doctor finds
  • tissue features of the nodule

Depending on how the cells look with a CT scan, doctors classify nodules as:

  • solid
  • subsolid
    • ground-glass
    • part-solid

Here’s a look at the Fleischner Society guidelines for each type.

Recommendations for single solid nodule

Size Treatment
Smaller than 6 mmlow risk: no routine follow-up needed
high risk: optional CT scan at 12 months
68 mmlow risk: CT scan at 6–12 months and possibly at 18–24 months
high risk: CT scan at 6–12 months and again at 18–24 months
Greater than 8 mmCT scan at 3 months and possibly PET-CT scan or biopsy

Recommendations for multiple solid nodules

SizeTreatment
Smaller than 6 mmlow risk: no routine follow-up needed
high risk: optional CT scan at 12 months
Greater than 6 mmlow risk: CT scan at 3–6 months and possibly at 18–24 months
high risk: CT scan at 3–6 months and again at 18–24 months

Recommendations for single subsolid nodules

SizeTreatment
Ground-glass nodule smaller than 6 mmno follow-up required
Ground-glass nodule greater than 6 mmCT scan at 6–12 months and every 2 years for 5 years if they persist
Part-solid nodule greater than 6 mmCT scan at 3–6 months
CT scan every year for 5 years if solid component remains under 6 mm

Recommendations for multiple subsolid nodules

SizeTreatment
Smaller than 6 mmCT scan at 3–6 months
if stable, CT scan at 2–4 years in high-risk people
Greater than 6 mmCT scan at 3–6 months
management based on the most suspicious nodule

A doctor may recommend a biopsy if repeat CT scans show that the nodule is getting bigger over time or has concerning features.

A biopsy can be performed in several ways:

  • with a long tube that goes down your throat called a bronchoscope
  • with a hollow needle through your chest wall with CT guidance
  • with surgery to remove the nodule and surrounding lung tissue

Risk factors for the development of cancerous lung nodules include:

You may be able to minimize your chances of developing lung nodules by quitting smoking if you currently smoke or by avoiding smoking if you don’t. This can be difficult, but a doctor can build a cessation plan that works for you.

Minimizing your exposure to cancer-causing substances like uranium and wearing proper safety equipment when you do handle them may also lower your risk.

Lung nodules are small growths in your lungs less than 30 mm in diameter. The majority of these nodules aren’t cancerous, but the risk becomes higher with increased size.

A doctor may want to perform regular follow-ups for nodules larger than 6 mm or for smaller nodules if you have a high risk of lung cancer.

A doctor may recommend a biopsy or surgical removal of nodules that are growing or have concerning features.