What Is a Lung Nodule?

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Hearing your healthcare provider say you have a lung nodule or lung nodules may sound scary. Still, these small, abnormal lesions are common and usually aren't worrisome. About 95% of lung nodules found on first-time CT scans are not cancerous.However, it’s essential to follow through on getting a diagnosis, even if you’ve never smoked.

This article will explain what causes lung nodules, how they are diagnosed, the risk of your lung nodule being cancerous, and how they are treated.

Definition

Lung nodules look like "spots" on X-rays and CT scans. They are sometimes also referred to as "coin lesions" because of their round, coin-like shape.

Lung nodules are three centimeters (cm) or 1.2 inches in diameter or less. They need to be at least 1 cm in size before they can be seen on a chest X-ray. CT scans provide more finely detailed images and can detect nodules as small as 1 to 2 millimeters.  

Lesions larger than 3 cm are referred to as lung masses, not nodules, and have a greater risk of being cancerous.

Prevalence

Lung nodules are common. They are found on one in 500 chest X-rays and one in 100 CT scans of the chest. Approximately 150,000 lung nodules are detected in people in the U.S. each year. Roughly half of adults who get a chest X-ray or CT scan have them.

lung nodule causes

Verywell / Emily Roberts

Symptoms

Lung nodules are so small that they don't tend to cause breathing problems or other symptoms. That's why they're usually found “accidentally” or "incidentally" when a chest X-ray is done for some other reason.

If symptoms are present, they may include:

  • A cough
  • Coughing up blood
  • Wheezing
  • Shortness of breath, often mild at first and only with activity
  • Respiratory infections, if the nodule is located near a major airway

Causes

Lung nodules can be either benign, which means noncancerous, or malignant, which means cancerous. Most benign lung nodules are the result of inflammation from infections or illnesses.

When your lungs become inflamed, tiny masses of tissue can develop.  Over time, the clumps can harden into a nodule on your lung.

The causes of most benign lung nodules can be broken down into a few major categories.

  • Infections, including bacterial infections such as tuberculosis and pneumonia; fungal infections from breathing in spores found in bird or bat droppings, or moist soil, wood, and leaves; and parasitic infections such as roundworms and tapeworms
  • Inflammation from irritants in the air, air pollution, or autoimmune conditions such as rheumatoid arthritis or sarcoidosis
  • Scarring from surgery or chest radiation

Other, less-common causes of a lung nodule include:

  • Pulmonary infarctions: areas of lung tissue that have lost their blood supply)
  • Arteriovenous malformations: a type of blood vessel abnormality
  • Atelectasis: collapse of part of a lung
  • Pulmonary fibrosis: thickening, scarring of lung tissue
  • Amyloidosis: build up of a kind of protein in the lung

The most common causes of malignant lung nodules are lung cancer or cancers from other regions of the body that have spread to the lungs.

  • Malignant tumors: Cancers first detected as nodules include lung cancer, lymphomas, sarcomas, carcinoid tumors, a kind of neuroendocrine tumors. 
  • Metastases: Nodules could be other cancers, such as breast cancer, colon cancer, bladder cancer, and prostate cancer, that have spread to the lungs. When a nodule is due to a metastasis from another cancer, there are often multiple lung nodules present.

Diagnosis

There are three diagnoses for lung nodules; noncancerous, cancerous, or indeterminate. When healthcare providers see a lung nodule on an X-ray, the first thing they usually do is get any previous X-rays you may have had and compare them.

If the nodule has been there for a long time and hasn't changed, it's probably not cancer. Further tests may not be needed. However, if you don’t have any prior X-rays for comparison, the nodule has changed, or the nodule is new, further tests may be needed.

Your healthcare provider will also get a detailed medical history from you. The questions will zero in on risk factors you may have for any type of lung nodules.

Examples of some of the questions you might be asked include:

  • Do you smoke? Have you ever smoked?
  • Have you had tuberculosis, pneumonia, surgery or chest radiation?
  • What kind of work do you do?
  • Have you been exposed to asbestos or radon?
  • Do you work outdoors?
  • Where have you traveled?

For example, if you work outdoors with moist wood or soil, live in the southwest, or have traveled to certain countries, a fungal or parasitic infection may be the cause of your lung nodule. Whereas if you smoke or used to smoke, a malignant tumor could be a possibility.

If a nodule does not appear to have changed or your healthcare providers believe that there's a low risk of it being cancer, they may take a "wait and watch" approach. They will have you get another imaging test in six months to a year. Single, solitary nodules that have remained unchanged for two or more years do not generally need any further workup.

Imaging Tests

If your nodule is found on a chest X-ray, the first step will usually be to do a computed tomography (CT) scan of your chest. CT scans can provide images with a greater level of detail and taken at different angles. This is important because small cancers can be missed on a chest X-ray.

Other tests healthcare providers may order include:

  • MRI (magnetic resonance imaging): This imaging test uses magnetic fields and radio frequencies to provide your healthcare provider with a more highly detailed look at your nodule.
  • PET (positron emissions tomography) scan: Unlike CT scans and MRI which are "structural" tests, a PET scan is a "functional test." It helps tell what is happening inside a nodule. These tests are especially helpful for those who have had previous chest radiation, lung infections, or surgery, which may result in scar tissue. 

The number of lung nodules that are read by radiologists as "indeterminate," meaning the diagnosis is unclear, has increased with the use of lung cancer screening. Hearing that your nodule or nodules are indeterminate can be confusing.

Unfortunately, there are times when it is impossible to know whether a nodule is malignant based on imaging tests alone. In order to answer this question, a biopsy must be done. Thankfully, radiologists, surgeons, and pathologists together are finding less invasive methods of sampling and analyzing tissue.

Biopsy

If your nodule has changed in size or appearance, your diagnosis is uncertain, or there's a chance your nodules might be metastatic cancer from another tumor, a sample of your nodule may be required to determine whether it is malignant.

There are different ways to get this sample:

  • Needle Biopsy: You'll be given a local anesthetic. Your healthcare provider will use CT scan images or even a kind of X-ray movie to guide the needle through your chest to get a tissue sample of your lung nodule.
  • Bronchoscopy: You'll be sedated. Your healthcare provider will run a long, thin fiberoptic tube with a surgical cutting tool on the end of it down your throat and into your lung to get a sample of your nodule for lab analysis.
  • VATS Biopsy: You're given a general anesthetic. Healthcare providers use a a special kind of video to assist in inserting a tube through the chest wall to get a sample of your lung nodule tissue for analysis. They can also remove the entire lung nodule.

Research suggests that even when a lung nodule is found in a person who might be expected to have lung metastases, only half of the nodules were metastases when biopsied. Up to 25%, rather, were a second primary lung cancer. 

Recap

To diagnose a lung nodule, your healthcare provider will first ask you about your history and risk factors. If the nodule was found on an X-ray, you may need other imaging tests to get more detailed pictures. In some cases, it's necessary to get and examine a sample of the nodule to confirm the diagnosis.

Risk of Cancer

Overall, there's a 60% chance that a lung nodule detected on an X-ray will be benign. There's a 99% chance that a lung nodule found on a CT scan is not cancerous.

However, a person's actual risk depends on a variety of factors, such as age. In people younger than 35, the chance that a lung nodule is malignant is less than 1%, while half of all lung nodules in people over 50 are cancerous.

Recap

Sixty percent of of lung nodules detected on an X-ray are benign, while 99% of lung nodules found on a CT scan are not cancerous.

Where you live and have traveled can play a role, too. For example, studies have found that lung nodules due to schistosomiasis, a parasitic infection, are fairly common in African immigrants. Likewise, nodules caused by fungal infections such as coccidioidomycosis are common in the Southwest.

Here are other factors that can play a role in whether lung nodules that show up on an X-ray are noncancerous or cancerous.

Low Risk of Lung Cancer
  • Under age 35

  • Nodule is small (less than 3 cm in diameter)

  • Patient is a nonsmoker (and has never smoked)

  • No exposure to toxins in the workplace

  • No history of lung cancer among family members

  • No other signs or symptoms of lung cancer

  • Nodules are smooth and round in shape

  • Nodules are only partly solid

  • Nodules do not get bigger over time

  • Nodules are calcified (contain calcium deposits)

  • Interior of nodule is "cavitary"—darker on X-rays

  • Only one or a few nodules are present

  • Nodules are located in the right or left lower lobes or the right middle lobes of the lung

High Risk of Lung Cancer
  • Over age 50

  • Nodule is larger than 3 cm in diameter

  • Patient smokes or is a former smoker

  • Exposure to occupational toxins such as asbestos or radon

  • First- or second-degree relative with lung cancer

  • Presence of lung cancer symptoms such as persistent cough or shortness of breath

  • Nodules are "spiculated"—have irregular or lobe-shaped borders

  • Nodules are solid

  • Nodules grow rapidly (on average doubling in size in four months)

  • Nodules show no signs of calcification

  • Nodules are not cavitary

  • Presence of multiple nodules (may indicate cancer metastases to the lungs)

  • Nodules are located in left or right upper lobes of the lungs

Lung Cancer Screening

Lung cancer screening has been found to decrease the mortality rate from lung cancer by 20%. 

U.S. health officials recommend that if you're between the ages of 50 and 80, if you still smoke, you quit within the last 15 years, or you have what they call a "20 pack-year smoking history," you should get screened every year for lung cancer.

This measurement is a way to gauge how much you've smoked in your lifetime. It means that if you smoked one pack a day for 20 years or two packs a day for 10 years, you should get tested every year for lung cancer.

The recommendations call for using low-radiation-dose CT scans. Screening with chest X-rays has not been shown to reduce the risk of dying from lung cancer.

As with any screening test, there is a risk of false positives, and it's common to find nodules on CT screening. Finding nodules does not always mean cancer. In fact, studies thus far estimate that only around 5% of nodules found on a first lung CT scan screening are cancerous.

Recap

If you're between the ages of 50 and 80, you smoke, you quit within the last 15 years, or you have a "20 pack-year smoking history," you should be screened for lung cancer every year. A 20 pack-year smoking history means that you smoked one pack of cigarettes a day for 20 years, or two packs a day for 10 years.

Treatment

The treatment of lung nodules varies widely depending on the diagnosis. Most benign lung nodules can be left alone, especially those seen on previous imaging tests that haven’t changed for two or more years.

If your nodule is cancerous, detection at this small size is very curable. In fact, treatment and survival rates for lung cancer, in general, have improved significantly in the past few years.

Summary

Nodules are "spots" in the lungs that are 3 cm in size or smaller. Most nodules are not cancerous, but rather caused by things like infection or scarring. They are more likely to be cancerous in people over age 50 and those who have smoked. Lung cancer screening is recommended for certain people who have a higher risk of lung cancer.

A Word From Verywell

If you've heard that you or a loved one have a lung nodule, you are probably feeling a combination of nervous and overwhelmed. There are so many different possibilities for diagnosis, and some are frightening.

As you undergo testing and wait for your diagnosis, it may help to know that most lung nodules are not cancer.

If your lung nodule is cancerous, it may be very curable. New technologies and treatments have significantly improved survival rates for people with lung cancer.

Lastly, if your nodule turns out to be lung cancer, reach out to family and friends for support and help. There is also an active lung cancer community that will welcome you.

Frequently Asked Questions

  • Can lung nodules be cancerous?

    Most lung nodules are not cancerous. Sixty percent detected on an X-ray and 99% detected on a CT scan are benign. However, sometimes, lung nodules can be small cancers. That's why it is important to follow though on a diagnosis.

  • Why do I have to get my lung nodule checked out if I have never smoked?

    Some lung nodules can be small developing cancers. Lung cancer is the leading cause of death due to cancer in the US. Up to one-fifth of US lung cancer deaths now occur among people who have never smoked or used any form of tobacco.

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