Lung Nodules

January 24, 2025

This page was reviewed under our medical and editorial policy by Jyoti Malhotra, M.D., M.P.H., associate professor, Department of Medical Oncology & Therapeutics Research, City of Hope^® Orange County Lennar Foundation Cancer Center; and Jae Y. Kim, M.D., associate professor, Division of Thoracic Surgery, Department of Surgery, City of Hope Cancer Center Duarte

Lung nodules are common, and they are found in up to half of people who have low-dose computed tomography (CT) imaging scans, according to the U.S. Department of Veterans Affairs. They are also sometimes called pulmonary nodules. If just one lung nodule is found, it is known as a solitary pulmonary nodule, or it might be called a “spot on the lung.”

What Is a Lung Nodule?

A lung nodule is a small round or oval lesion that is 3 centimeters or smaller. These lesions are often solid, with the same soft tissue structure throughout the entire nodule.

Sometimes the tissue structure is not the same throughout and the nodule is somewhat hazy. This is known as a ground-glass nodule.

If the nodule has both solid and ground-glass characteristics, it is called a part-solid nodule.

Are Lung Nodules Cancerous?

The majority of lung nodules are not cancerous. The doctor examines the lesion on an imaging test, such as a computed tomography (CT) scan, to help determine if cancer is present. Other diagnostic tests may be recommended as well.

Depending on the cancer risk, the doctor may also suggest follow-up imaging tests every few months to a year to see if the nodule grows and to monitor its characteristics for signs of malignancy (cancer).

Can Lung Nodules Turn Into Cancer?

While it is unlikely that a nodule on the lung is cancer, sometimes these lesions may develop into cancer. This is why evaluations and screenings like CT scans or chest X-rays are important for some people at risk.

During an evaluation, doctors typically ask about the patient’s history, including if he or she smokes (tobacco products), has symptoms of lung cancer, or a history of lung cancer or other lung conditions like emphysema or chronic obstructive pulmonary disease (COPD). A family history of lung cancer may also be used to determine the likelihood of a nodule turning into cancer.

Lung Nodule Symptoms

Pulmonary nodules usually do not cause symptoms. Although these nodules are sometimes found while screening for lung cancer, more typically they are discovered on a scan or X-ray done for other reasons, such as to detect lung infections or diagnose trauma.

What Causes Lung Nodules?

While the causes of lung nodules are not always known, they may develop because of:

• Past infections like tuberculosis or fungal infections
• Scar tissue
• Inflammatory conditions like rheumatoid arthritis
• Cysts or abnormal artery formations that are present at birth
• Irritants found in the air
• Cancer, especially primary lung cancer

Lung Nodules After COVID-19

Patients diagnosed with a COVID-19 infection may develop lung nodules, especially round or oval ground-glass nodules. In a small percentage of COVID-19 patients, nodules have been shown to look abnormal or atypical. If lung nodules do show concerning features, the patient’s doctor will likely recommend further tests to help evaluate whether they are cancerous or noncancerous.

Diagnosis and Testing

While many lung nodules are found on chest X-rays, CT scans tend to be better at detecting them. CT scans are a primary diagnostic imaging test used for monitoring and evaluating nodule size. Larger or fast-growing nodules are more likely to be malignant (cancerous) than smaller or slower-growing nodules.

Positron electron tomography (PET) scans are another testing option, and they are used to check lung nodules for cancer features, particularly if the nodule is large (bigger than about 0.8 centimeters) and the patient is considered to be at high risk for developing cancer.

If a nodule has grown in size, has features that may indicate cancer or if the person smokes tobacco or has symptoms of lung cancer, the doctor may schedule a biopsy. During a lung biopsy procedure, a sample of tissue from the lung nodule is taken. This may be done either with a needle through the skin (percutaneously) or transbronchially, which involves using robotic bronchoscopy.

The tissue sample is then viewed under a microscope by a doctor called a pathologist, who specializes in identifying diseases of the tissues and cells. The pathologist looks for signs of cancer or other lung problems like scar tissue to help determine the underlying cause of the nodule.

Lung Nodule Treatments

Treatment may not be necessary for lung nodules. Depending on the nodule’s size and appearance and the patient’s medical history and treatment preferences, the doctor may either recommend no follow-up exams or repeat CT scans to monitor it.

Sometimes a biopsy is recommended to help diagnose or rule out cancer. Nodule resection (removal) may also be suggested for patients who are considered at high risk for developing cancer.

When to Worry About Lung Nodules

For the majority of people, being diagnosed with a lung nodule is nothing to worry about. Cancer is found in fewer than 5% of lung nodules. However, since lung cancer is one potential cause of nodules, doctors assess certain factors to help understand whether cancer may be present.

Solid fat-filled or calcified nodules that are smaller, smoother, more concentric (circular or spherical) and slower-growing are typically less likely to be cancerous.

The following factors may indicate that a nodule is more likely to be cancer:

• Spikes or points on the nodule, known as spiculation or a spiculated mass
• Nonsolid features (such as a ground-glass or part-solid appearance)
• High growth rate
• Larger size

Does Location Matter?

Yes, lung nodule location matters. In addition to how fast a nodule grows and its physical features, location has been linked to a nodule’s likelihood of being either benign (noncancerous) or malignant (cancerous).

The lung is made up of sections called lobes. The left lung has two lobes, and the right lung has three. Most lung cancer occurs in the upper lobes of the lungs, and finding a nodule in one of these upper lobes may be an indicator that the nodule is more likely to be cancerous.

Does Larger Pulmonary Nodule Size Indicate Cancer?

When it comes to lung nodules and cancer, larger size is strongly linked to higher likelihood of cancer — but a bigger nodule may not necessarily mean cancer. Only a doctor who performs diagnostic testing of the nodule will be able to tell if it is cancerous.

At City of Hope, the team of lung cancer experts works to screen for lung nodules and quickly diagnose their underlying causes. If cancer is detected, a treatment plan is quickly created to help ensure the disease is addressed as early as possible.