Benign lung nodules can have a few different causes. These include current and past infections in the lungs and inflammation in the body from a condition like rheumatoid arthritis.

A lung nodule is a small growth in the lung that’s less than 3 centimeters. Most are benign (noncancerous) and don’t cause any symptoms.

Most lung nodules aren’t a cause for concern, but your doctor may wish to monitor a nodule with regular CT scans for a few years to see if it grows.

lung nodule on an x-ray, lung nodule size chartShare on Pinterest
A lung nodule detected in a chest X-ray. Lange123, CC BY-SA 3.0, via Wikimedia Commons.

Roughly 95% of people with a benign lung nodule that shows up on a diagnostic scan don’t have any symptoms. If you do have symptoms, they’re usually related to an underlying condition causing the nodule.

Following a CT scan, a doctor may be able to differentiate between a benign (noncancerous) and malignant (cancerous) nodule by its size and shape.

Benign nodules are usually round, smooth, smaller than 8 millimeters (mm), without a defined border, and calcified (hardened with calcium).

Malignant nodules are typically larger with a well-defined border, bumpy (lobulated) or spikey (spiculated), and irregularly shaped. They also tend to be present in the upper lobes of the lungs.

You can have one lung nodule (solitary lung nodule) or multiple nodules.

Benign pulmonary nodules can be due to inflammation from a number of conditions, including:

The most common cause of a benign nodule is a previous infection. In some cases, the cause of the lung nodule is unknown.

Lung nodules after COVID-19

Research suggests that 3–12% of people with COVID-19 infections have nodules on their CT scans.

Doctors discover most lung nodules incidentally during a CT scan or chest X-ray for another reason. They show up as white spots on the scan.

According to the American Thoracic Society, doctors find nodules in up to half of adults who get a chest X-ray or CT scan.

Most small lung nodules are benign and won’t ever become cancerous. But it’s possible for a benign lung nodule to become malignant over time.

A malignant nodule is more likely to occur:

  • if you’re older
  • if the nodule is large
  • if you smoke or have smoked in the past
  • if you have a family history of lung cancer
  • if you’ve had exposure to radon, asbestos, or secondhand smoke

If you have any of these risk factors, your doctor may want to monitor your nodule over time to see if it grows. Nodules smaller than 6 mm usually don’t require routine follow-up.

A nodule that grows over time could mean it’s malignant.

To diagnose a malignant nodule, a doctor may take a sample of the nodule (biopsy) to examine it under a microscope. Doctors don’t usually recommend biopsies when nodules are small.

Benign lung nodules usually don’t require treatment or removal. A doctor may order additional CT scans over the course of several months or years to monitor for any changes in the size of the nodule. This is known as active monitoring.

If nodules grow large enough to cause symptoms or are cancerous, a surgeon may need to remove them.

Benign lung nodules usually don’t grow. Even if they’re malignant, they’ll grow fairly slowly.

It takes several months for a nodule to get bigger. It’s considered safe to wait a few months for the next CT scan. Waiting shouldn’t affect your treatment or chances for a cure if the nodule turns out to be cancerous.

Here are answers to some frequently asked questions about benign lung nodules.

Can you have lung nodules that aren’t cancer?

Yes, you can have lung nodules that aren’t cancerous. In fact, more than 95% of lung nodules are noncancerous (benign).

Is it normal to have benign nodules on your lungs?

Benign pulmonary (lung) nodules are fairly common. Doctors find them in up to half of adults who get a chest X-ray or CT scan.

What are the odds of a lung nodule being cancerous?

Fewer than 5% of lung nodules turn out to be cancerous.

When should you worry about lung nodules?

Most lung nodules are benign and not a cause for concern. If the nodule gets larger over time, it could be a sign of cancer.

Can lung nodules disappear on their own?

Most lung nodules don’t change over time, but they can get smaller or even disappear on their own.

Do doctors need to remove benign lung nodules?

Benign lung nodules usually don’t require treatment or removal. A doctor may recommend surgery to remove a nodule if it grows over time or becomes cancerous.

Benign lung nodules are small growths that form in the lungs. The vast majority of lung nodules aren’t cancerous, and most don’t cause any symptoms or require treatment.

If your doctor finds a nodule on your lung during a CT scan or chest X-ray, they may recommend follow-up scans to see if the nodule gets bigger over time.