A lung nodule is a small growth in the lung that can show up on a CT scan. Many are benign or noncancerous and do not spread to other parts of the body. However, some are malignant or cancerous.

Lung nodules, also known as pulmonary nodules, are very common. Often, these small growths are visible on a CT scan. These nodules often do not cause symptoms. However, if a person presents with symptoms of a respiratory illness or infection, a doctor may request a CT scan. Fortunately, most pulmonary nodules are benign, meaning they are not 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 lung nodule does not always indicate lung cancer, and most of these nodules are noncancerous.

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

  • Current infections: Infectious illnesses that affect the lungs, such as tuberculosis or fungal infections, can cause inflammation. A cluster of cells called a granuloma may form in an inflamed area, giving the appearance of a nodule.
  • Past infections: An area of scarring from a previous infection can also show up as a nodule on a scan.
  • Noninfectious inflammation: Inflammation that does not stem from an infection can also form nodules in the lung. The underlying cause may be rheumatoid arthritis or sarcoidosis, for example.
  • Noncancerous tumors: Other noncancerous growths, such as a pulmonary hematoma, may develop in the lung.

If a lung nodule is malignant, prompt treatment is necessary.

If any growth in the lung is larger than 3 centimeters (cm), about 1.2 inches, doctors refer to it as a “mass.” Lung masses are more likely to be cancerous, so doctors consider them to be indications of cancer unless testing shows that they are benign.

Around 95% of pulmonary nodules cause no symptoms. These growths are usually too small to interfere with breathing.

However, the underlying health issue responsible for the nodule may cause symptoms. For example, if a person has an infection, they may have a fever, a cough, and a general feeling of being unwell.

Most people with lung cancer have no symptoms until the cancer has spread. If the disease does cause symptoms at an early stage, they may include:

  • shortness of breath
  • wheezing or hoarseness
  • chest pain that gets worse with deep breathing, laughing, or coughing
  • coughing up blood or rust-colored phlegm
  • back pain
  • unexplained weight loss
  • weakness or fatigue

The following factors increase the likelihood of developing a malignant lung nodule:

  • previous or current smoking
  • older age
  • a personal or family history of cancer
  • another lung disease, such as chronic obstructive pulmonary disease, better known as COPD
  • exposure to asbestos, soot, radon, diesel fumes, arsenic, cadmium, or nickel

Larger pulmonary nodules are more likely to be cancerous. According to a 2019 review, if a nodule is smaller than 0.6 cm, there is less than a 1% risk of it being cancerous.

In addition, nodules in people with weakened immune systems are more likely to be malignant.

If possible, doctors look at previous imaging studies to see whether a nodule has grown. If a nodule visible on a past scan has not grown, it is not likely to be cancerous.

When a person has symptoms of a respiratory illness or infection, a doctor usually requests a chest X-ray or a CT scan. A CT scan gives a more detailed image and can show nodules smaller than 1 cm.

If there is a questionable spot or shadow on a chest X-ray, the doctor may request a CT scan. This can confirm that there is a nodule and show its size and appearance.

In adults, pulmonary nodules are visible on up to 50% of chest CT scans. Fortunately, fewer than 5% of lung nodules turn out to be cancerous.

Some characteristics of a nodule, such as a larger size or a prickly or spiked border, indicate that it is more likely to be cancerous.

When assessing the risk of cancer, a doctor also considers a person’s medical history, including their smoking history.

Is a biopsy necessary?

A doctor does not always need a biopsy when they find a pulmonary nodule. If the person’s risk of cancer is low and the characteristics 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 it can cause complications such as bleeding or a collapsed lung.

Still, when the features of the nodule suggest malignancy, the doctor may recommend a biopsy. This involves removing a small amount of tissue from the nodule.

When possible, a multidisciplinary team including a radiologist, thoracic surgeon, pathologist, and pulmonologist discusses the safest way to obtain the biopsy.

The best approach may be bronchoscopy, which involves inserting a thin, tube-like scope through the mouth or nose, down the windpipe, and into the lung. The scope has a small camera, which allows the doctor to view the airways. They then use special tools to obtain a tissue sample from the nodule.

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

The choice of procedure depends on the size and location of the nodule. After obtaining the sample, the doctor sends it to a laboratory, where a pathologist examines it to look for cancerous cells.

The best treatment for a lung nodule often depends on whether it has features that suggest the risk of cancer.

Treatment for a noncancerous nodule

If the nodule presents a low risk of cancer, the doctor may recommend monitoring the nodule with regular CT scans for 2–5 years to identify any possibly malignant changes, such as an increase in size.

A doctor considers various factors when determining the right frequency of follow-up scans. These factors include the person’s overall risk of cancer and the size of the nodule.

If the lung nodule does not grow, it is unlikely to be cancerous. In this case, further imaging tests may not be necessary.

If a pulmonary nodule has developed due to an ongoing infection, such as tuberculosis, treating the infection is the best approach.

Treatment for a cancerous nodule

If biopsy results show that the nodule is cancerous, treatment options depend on the type and stage of the cancer. The doctor may adapt the treatment if the person’s condition improves.

A doctor may request a thoracotomy to remove a cancerous nodule. This surgical procedure involves removing the nodule through an incision in the chest wall.

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

Depending on the cause, it may not be possible to prevent lung nodules.

Smoking is one of the main risk factors for lung cancer, and around 90% of lung cancer cases develop due to smoking. As a result, quitting smoking reduces the risk of malignant pulmonary nodules.

Other ways to lower the risk include:

  • avoiding exposure to radon
  • avoiding air pollution, such as by taking steps to lower levels of air pollution inside the home
  • taking steps to prevent exposure to hazardous chemicals, such as asbestos, arsenic, or chromium, at work

Learn more about preventing lung cancer.

Some FAQs about lung nodules may include:

Can a CT scan tell if a lung nodule is cancerous?

A CT scan can show if there is a nodule present, as well as its size and appearance. A CT scan itself cannot confirm if the nodule is cancerous. Some characteristics, such as a larger size or a prickly or spiked border, may indicate that it is more likely to be cancerous. As such, another test, such as a biopsy, is necessary to confirm if the lung nodule is cancerous.

Will lung nodules go away?

In most cases, pulmonary nodules will either stay the same size, get smaller, or go away. A doctor may recommend nodule surveillance, or active monitoring, to check the size of the nodule over several follow up scans.

When should I worry about lung nodules?

Most lung nodules are benign, meaning they are not cancerous. If a doctor identifies a pulmonary nodule, they may suggest nodule surveillance. If while monitoring the nodule, they notice changes such as an increase in size, or a prickly border, they may request further testing to see if it is cancerous.

Can you live a long life with lung nodules?

In many cases, pulmonary nodules are benign. With noncancerous lung nodules, a person will not typically require any further treatment or experience complications.

With cancerous lung nodules, the prognosis can vary depending on a number of factors, such as the stage of the condition.

Noncancerous lung nodules usually require no further treatment and do not cause complications.

The outlook for people with cancerous pulmonary nodules varies, depending on the stage of the disease. In many cases, early detection and treatment improve the long-term outlook. Cancer specialists can provide more information for each person.