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.
In this article, we look at the possible causes of lung nodules, their symptoms, and how doctors diagnose and treat them.
A lung nodule does not always indicate lung cancer, and most of these nodules are noncancerous.
Noncancerous lung 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.
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.
- 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 lung 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.
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 lung 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
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 lung 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.
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 lung 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
Noncancerous lung nodules usually require no further treatment and do not cause complications.
The outlook for people with cancerous lung nodules