A lung nodule is a small growth on the lung and can be benign or malignant. The growth usually has to be smaller than 3 centimeters to qualify as a nodule.

Benign nodules are noncancerous, typically not aggressive, and do not spread to other parts of the body.

Malignant nodules are cancerous and can grow quickly. They can spread to other nearby tissues and distant organs.

Doctors usually call growths that are larger than 3 centimeters (cm) lung masses, and these typically have a higher chance of being cancerous.

In this article, we look at the possible causes of lung nodules, their symptoms, and how doctors diagnose and treat them.

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A person with lung nodules may experience chest pain and breathlessness.

Although the diagnosis of any growth in the lung can be frightening, a lung nodule does not always indicate lung cancer.

Lung nodules are very common. According to the American Thoracic Society, lung nodules are visible on up to 50% of chest CT scans in adults. Fewer than 5% of lung nodules end up being cancer.

Noncancerous lung nodules can have a variety of causes, including:

  • Infection: Inflammation in the lungs might occur due to a range of infections, such as tuberculosis (TB) or fungal infections. A group of cells called a granuloma may develop around the inflamed area in the lung. Sometimes, nodules represent an area of scarring from a previous infection.
  • Noninfectious inflammation: Inflammation that does not occur due to an infection can also lead to nodules in the lung. Rheumatoid arthritis (RA) or sarcoidosis, for example, can contribute to noninfectious inflammation.
  • Noncancerous tumors: Other noncancerous growths may also develop in the lung. One example of this is a fibroma, which is a benign growth of connective tissue.

Although most lung nodules are not cancerous, some turn out to be malignant and require prompt treatment.

Certain risk factors increase the chances that a lung nodule is malignant, including:

  • having a history of smoking
  • being an older adult
  • having a family or personal history of cancer

Larger lung nodules are also more likely to be cancerous.

A lung nodule often does not cause symptoms. These small growths are usually not large enough to interfere with breathing.

Symptoms of the condition that is causing the nodule may occur, however. For example, if a lung nodule is due to lung cancer, symptoms may include:

  • breathlessness
  • chest pain
  • coughing up blood
  • back pain
  • weight loss

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A doctor may order imaging scans if they suspect lung nodules.

When a person has symptoms of respiratory illness or infection, a doctor will usually request a chest X-ray or a CT scan. A lung nodule will often be visible on one of these scans.

The nodule will show as a spot or shadow on the X-ray. If an X-ray shows signs of a nodule, the doctor may request a follow-up CT scan. This type of imaging test can provide more detail than an X-ray.

After finding a lung nodule, the doctor will assess its size, shape, and appearance. Certain features may suggest that the nodule is more likely to be cancerous. For example, larger nodules are more likely to be cancer.

The location, shape, and size of the nodule may increase its risk of malignancy. The doctor will also consider the person's medical history, including their smoking history, to evaluate the risk of a cancerous nodule.

Do I need a biopsy?

When the features of the nodule suggest malignancy, the doctor may recommend a biopsy. This procedure involves removing a small amount of tissue from the nodule, either using a needle or during a bronchoscopy.

A bronchoscopy involves inserting a thin tube down the windpipe and into the lung through the mouth or nose.

The tube has a small camera, which allows the doctor to view the airways. They will then use special tools to obtain a tissue sample from the nodule.

Another option is a needle biopsy, which involves inserting a needle into the lung through the chest wall. A doctor will usually use a CT scan to guide the insertion.

The procedure healthcare providers use to access a tissue sample depends on the size and location of the nodule.

After obtaining the sample, the doctor sends the tissue to a laboratory. A pathologist will examine the tissue under a microscope to look for cancerous cells.

A doctor will not always need to perform a biopsy when a person shows lung nodules. If an individual is low risk, and the features of the nodule suggest a low likelihood of cancer, a biopsy may cause more harm than good.

Performing a biopsy on a small lung nodule can be difficult, and complications, such as bleeding or a collapsed lung, might occur.

Read more about lung biopsies here.

Treatment for lung nodules will often depend on whether they have features that present a cancer risk.

Treatment for a noncancerous nodule

If the nodule has characteristics that suggest a low risk of cancer, the doctor may recommend watchful waiting. This approach involves monitoring the nodule with regular CT scans over time to identify any potentially malignant changes, such an increase in size.

Watchful waiting may continue for a few years to make sure the nodule does not grow. The doctor will use various factors to determine how frequently a person needs follow-up scans. These factors include a person's overall risk of cancer and the size of the nodule.

If the lung nodule does not change over about 2 years, it is unlikely to be cancerous. In this case, further imaging tests may not be necessary.

If a lung nodule has developed due to an active infection, treating the underlying disease is the best way to manage the nodule.

An example of this is when a nodule is due to tuberculosis, and a doctor prescribes a course of treatment for the infection.

Treatment for a cancerous nodule

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A thoracotomy can remove a cancerous nodule.

When a lung nodule is malignant, it is most often due to lung cancer, lymphoma, or cancer that has spread to the lung from another organ.

If biopsy results determine that the nodule is cancerous, treatment options depend on the type and stage of the cancer. The doctor may also change the management methods during the treatment if the individual improves.

In some instances, a doctor may request the removal of a cancerous nodule using a thoracotomy. This is a surgical procedure in which a surgeon makes a cut through the chest wall into the lung to remove the nodule.

Additional treatment for cancerous lung nodules may include chemotherapy, radiation therapy, and other surgical interventions.

The outlook for people with a malignant lung nodule varies, depending on the stage of the disease. In many cases, early detection and treatment improve a person's long term outlook.

Noncancerous lung nodules have a good outlook and usually do not cause any complications. Depending on the cause, it may not be possible to prevent lung nodules.

Smoking is one of the main risk factors for lung cancer. According to the American Lung Association, around 90% of lung cancer develops due to smoking.

As a result, quitting smoking may prevent malignant lung nodules.

Here, learn more about preventing lung cancer.