What are lung nodules?

They are small masses of tissue in the lung that appear as round, white spots on a chest X-ray or CT scan. Because lung nodules rarely have symptoms, they are usually found incidentally in imaging done for other conditions, like a respiratory illness. According to the American Thoracic Society, nodules are found in up to half of adults who get an X-ray or CT scan.

Most are less than 10 millimeters (mm) — smaller than a green pea. Larger lung nodules, or those located near an airway, may cause symptoms such as:

• Chronic cough
• Blood-tinged mucus and saliva
• Shortness of breath
• Fever or wheezing

“Nodules identified on chest X-ray typically require additional evaluation, such as follow-up or other testing, to determine what they represent,” says Eric M. Hart, MD, a thoracic imaging radiologist at Northwestern Medicine. “Small (less than 6 mm) nodules are commonly identified incidentally on chest CT scans for reasons like chest pain or shortness of breath, or to evaluate for pulmonary embolism. The significant majority are benign, although in certain instances they may require follow-up to prove that.”

What causes lung nodules?

There are many reasons why a nodule might develop in the lungs. The most common causes include:

• Infections, such as tuberculosis, pneumonia and fungal infections
• Inflammatory conditions, such as pulmonary sarcoidosis and rheumatoid arthritis
• Noncancerous tumors, such as hamartomas
• Lung tissue scarring from previous illness or surgery
• Inhaling asbestos, coal dust, cigarette smoke, and other irritants or chemicals

Malignant (cancerous) lung nodules are the result of cancer that either starts in the lungs or spreads to the lungs from a cancer elsewhere in the body.

How are they discovered?

Lung nodules are usually found during imaging tests, such as:

• Chest X-ray, which may show larger nodules
• CT scan, which can provide a more detailed picture of the lungs and detect smaller nodules

Low-dose CT scans, which are used to screen people who are at a higher risk for lung cancer, can also detect nodules.

When found, nodules are evaluated by their size, shape, borders and composition, which helps your physician determine the cause and treatment, if needed. If the nodule appears suspicious, a biopsy may be ordered. A positron emission tomography (PET) scan may also be ordered to show the cellular activity of a nodule and help determine if it is cancerous.

For probable benign lung nodules, your physician may suggest CT scans to monitor the growth over time as a precaution. Nodules that stay the same size over a two-year period are typically considered noncancerous.

Your radiologist will report the results of your exam and recommend specific follow-up care to you and your physician. Follow-up care will be determined by nodule size, what it looks like and what it consists of. 

What are they made of?

Nodules can either be calcified or non-calcified.

Calcified nodules:

• Contain calcium deposits, making them dense and easily seen on scans
• Are usually not cancerous
• May occur after a lung infection
• Can be made of normal tissues in an abnormal location
• May need to be removed if they are larger or affect your health

Non-calcified nodules:

• Lack significant calcium deposits
• Are often caused by a past infection or inflammation
• May appear either solid or non-solid in imaging

What are my treatment options?

• Benign lung nodules typically do not require treatment unless they are large enough to cause breathing problems.
• Nodules caused by infection may be treated with prescribed antibiotics or antifungal medications.
• Cancerous lung nodules, especially when detected early, can often be surgically removed.
• If cancer has spread or is advanced, other treatments like chemotherapy and radiation therapy may be used.

Although it can be scary to learn you have lung nodules, they’re quite common and generally do not indicate lung cancer. Your physician will work with you to monitor your condition regularly.