Lung nodules

This page was reviewed under our medical and editorial policy by

Peter Baik, DO, Thoracic Surgeon

This page was updated on September 27, 2022.

It’s not uncommon to find a lung nodule. In fact, roughly 50 percent of adults who undergo CT scans have at least one lung nodule, according to the American Thoracic Society (ATS).

What is a lung nodule?

Lung nodules (also called pulmonary nodules) are spots or shadows that may show up in the lung during a chest imaging study, usually a CT scan. A lung nodule typically appears as a white spot and is under three centimeters in size. Nodules larger than three centimeters are considered lung masses.

Possible lung nodule causes

Although a lung nodule could be an early cancer, less than 5 percent of small nodules turn out to be early lung cancer (malignant nodule), according to the ATS.

Other, more likely causes of lung nodules include:

  • Noncancerous (benign) tumors or cysts
  • Inflammatory diseases
  • Scar tissue from an old infection
  • Congenital lung abnormalities

Lung nodule symptoms

Lung nodules are often too small to cause symptoms like pain or breathing problems. In some cases, however, they may press on airways or other structures, depending on the nodule's size and location.

To reduce the risk of developing lung cancer, quit smoking and let the doctor know if any of these symptoms occur:

  • A change or increase in cough
  • Coughing up blood
  • Shortness of breath
  • Chest pain
  • Unintended weight loss of 10 pounds or more

How are lung nodules diagnosed?

Most lung nodules are found when an imaging study is done to evaluate chest symptoms or as part of a lung cancer screening exam.

What happens after a pulmonary nodule is discovered depends on three factors:  

Because a biopsy can cause complications like bleeding, infection or a collapsed lung, it’s only done if the risk of cancer is high enough to justify the risk of biopsy.

Assessing the risk

Nodule size is the most important factor in assessing risk. Based on a review in Annals of Thoracic Medicine, nodules that are smaller than 6 millimeters have a less than 1 percent risk of being cancerous.

Lung nodule size chart

This chart shows the possible cancer risk related to lung nodules, based on size, that the care team may consider.

Lung nodule diameter Possible cancer risk
2 mm or smaller The risk of cancer is very small in these routine nodules
2 to 6 mm The risk of cancer is 1 percent or lower
6 to 8 mm The risk of cancer is 2 percent or lower
8 to 10 mm The risk of cancer is between 9 percent and 10 percent
Larger than 10 mm The risk of cancer is approximately 15 percent

Other factors for assessing risk

One of the most important things that doctors do to evaluate a nodule is look at any available old lung imaging studies. If a nodule was present in a past study and it hasn’t grown over time, it’s unlikely to be cancerous. 

Nodules that show strands extending out from the edges of the nodule—called spiculations—are more concerning for malignancy.

Personal risk factors for lung cancer are also important to consider. These risk factors may increase the risk of a nodule being cancerous:

  • History of smoking
  • Radon exposure
  • Older age
  • A history of previous cancer, including lung, head and neck, breast or colon cancer
  • A family history of lung cancer
  • A history of treatment with radiation therapy or chemotherapy for lymphoma
  • Occupational exposure to dusts, metals or fumes that have been linked to lung cancer
  • Lung disease, like COPD or pulmonary fibrosis

Does the lung nodule location matter?

The location of the lung nodule may guide the care team in evaluating possible risk, and studies indicate that nodules in the upper lobe may be more indicative of cancer. However, not all nodules in the upper region of the lung are cancerous, and not all nodules located elsewhere are benign. That's why it's important to follow the care team's recommendations on further testing and evaluations, no matter where the nodule is located.

Managing lung nodules

Once the care team has evaluated the risks, options may include no additional tests, scheduling a follow-up CT scan, scheduling a more sensitive imaging scan (PET scan), or performing a biopsy to diagnose the nodule. Some of the options are:

  • If the patient is young and the nodule is small, or a past imaging study shows no change in the nodule over two years, he or she may not need any further evaluation.
  • If the doctor thinks a nodule is at all suspicious, the patient may have another CT scan scheduled in a few months to see if the nodule is growing.
  • If the nodule is larger, the doctor may order a PET scan, because this type of study helps the doctor determine if the nodule is metabolically active.
  • If the nodule is high risk or if it grows on a follow-up imaging study, the doctor may schedule a lung biopsy.

Follow-up care

A biopsy involves taking a sample of cells from a nodule, so cells can be checked under a microscope for signs of cancer (pathology exam). The biopsy may be taken through a tube placed down into the lung, called a bronchoscopy. If the nodule is in an outer area of the lung, a needle may be placed through the chest into the lung to sample the tissue. If a nodule is very suspicious or difficult to reach, open surgery may be done to remove the nodule.

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Show references
  • American Thoracic Society (2020, June). What is a lung nodule?
  • Annals of Translational Medicine (2015, Feb. 3). Probability of lung cancer based on the size threshold and volume-doubling time for lung nodules detected in low-dose CT screening.
  • New England Journal of Medicine (2013, Sept. 5). Probability of Cancer in Pulmonary Nodules Detected on First Screening CT.