Lung nodules are common and usually develop after an injury or infection. However, in a small number of cases, they may be a sign of lung cancer.

Lung nodules can vary in size and shape. They can appear as sharp or blurry areas in the results of a CT scan.

While lung nodules are not usually a cause for concern, doctors may want to repeat a person’s CT scan or perform additional tests to rule out lung cancer.

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Lung nodules are formations with a rounded or irregular shape that healthcare professionals may notice on the results of a radiological imaging test. They typically have a diameter of 3 centimeters (cm) or fewer.

These nodules may be a sign of an old lung injury or infection and are not usually a cause for concern.

However, healthcare professionals may recommend repeating the imaging test, such as a CT scan, after a few months or 1 year to check if the nodule is growing. Whether they make this recommendation depends on various factors related to the nodule, such as its:

  • location
  • shape
  • size
  • appearance (hazy or solid)

In most cases, lung nodules that appear on CT scans are not cancerous. Usually, nodules result from previous infections and injuries that have caused scar tissue growth in the lungs.

However, healthcare professionals may still recommend a person with a nodule undergoes another CT scan after a few months to check if the nodule has grown to ensure it is not a tumor.

If the nodule has grown during the period between scans, doctors will perform more tests.

Only about 5% of lung nodule cases turn out to be cancerous.

It is common for lung nodules to appear during a CT scan that people undergo for reasons unrelated to cancer screening or the diagnosis of lung conditions.

Every year, healthcare professionals find lung nodules in about 30% of people who undergo CT scans of the chest.

Nodules can form due to the following factors:

  • trauma
  • lung infections
  • heart disease

Healthcare professionals refer to these lung nodules as “incidental pulmonary nodules.” They are rarely related to cancer.

If a doctor has concerns about a lung nodule, they may recommend a person undergoes another chest CT scan after a set time. This allows the doctor to check whether the nodule has grown within this period.

If the nodule has grown, the doctor may order a positron emission tomography (PET) scan, another type of imaging test, which usually helps them identify whether an atypical growth is cancerous.

The doctor may also want to collect a sample of tissue from the nodule through a prodedure called a biopsy. This involves passing a thin tube with a light and a camera, called a bronchoscope, down the person’s throat to reach the nodule and remove some tissue.

If the lump is on the outer side of the lung, the doctor may pass a thin needle through the chest wall to reach the nodule with the guidance of a CT scan.

If the doctor thinks there is a high chance the lung nodule is cancerous or if they cannot reach it with a bronchoscope or needle, a person may have to undergo surgery. A surgeon can remove the nodule, its surrounding tissue, and, if necessary, a larger section of the lung.

If a lung nodule is a tumor, a doctor will advise the individual about available treatment options based on the location, size, and stage of the cancer.

These options may include:

The specialist can also provide advice about the possible complications and side effects of each treatment to help a person consider which option is most appropriate for them.

What are the symptoms of a cancerous lung nodule?

People with cancerous lung nodules may develop symptoms of lung cancer, such as:

  • shortness of breath, coughing, or wheezing that does not go away or becomes worse
  • chest pain, especially when coughing or breathing deeply
  • recurrent chest infections, such as bronchitis or pneumonia
  • coughing up blood

What makes a lung nodule suspicious?

A lung nodule may be suspicious if it has a diameter larger than 3 cm or if it grows over time.

What size of lung nodule is worrisome?

A lung nodule that has an irregular shape or is bigger than 3 cm may be a sign of cancer. However, a person will need to undergo additional tests to determine whether a lung nodule is cancerous or not.

How often do lung nodules turn into cancer?

About 95% of lung nodules are benign, having developed due to an injury or a previous infection. Only about 5 lung nodules out of 100 turn into cancer.

Lung nodules are a common finding in CT scans. In most cases, lung nodules are from an old injury or infection and not a cause for concern.

Only about 5% of lung nodules turn out to be cancerous. If a doctor suspects a person may have a tumor, they may recommend attending a lung cancer screening test and undergoing a PET or CT scan after a few months to check whether the lung nodule has grown.