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What Are Solitary Pulmonary Nodules?

Could it Be Cancer?


Updated February 24, 2013

Every year in the U.S., more than 150,000 people will be told they have a solitary pulmonary nodule, and this is expected to increase as more people have screening tests for lung cancer. What does it mean if you are diagnosed with a solitary pulmonary nodule?

What Is a Solitary Pulmonary Nodule?

A solitary pulmonary nodule is defined as a single nodule (abnormality) seen on an x-ray or CT scan, that is less than or equal to 3 cm (1 ½ inches) in diameter. If a "spot" on the lung is larger than 3 cm it is considered a lung mass. The nodule is surrounded by normal tissue, and no other signs that might suggest cancer (such as enlarged lymph nodes or a pleural effusion) are present. Solitary pulmonary nodules are usually found incidentally, when an x-ray is done for another reason. They are fairly common, being found on roughly 1 in every 500 chest x-rays done.

If more than one nodule is present, the possible causes and recommended tests may be different:

What Are Possible Causes?

There are many causes of solitary pulmonary nodules (SPN), some being more common depending upon age and geographical location. Some of these include:

What Are the Chances it Means Cancer?

Overall, the chance that a solitary pulmonary nodule is cancer is around 40%, but this varies depending upon several factors:
  • Age – In younger people, a SPN is more likely to be benign, whereas in individuals over age 50, they are more likely to be malignant (cancerous).

  • Tobacco use – A history of smoking raises the likelihood that a SPN is malignant.

  • A history of cancer – Having a history of any type of cancer makes it more likely that a SPN is cancer.

  • Geographical location/foreign travel – In regions of the world where the infections above are common, a SNP is more likely to be due to an infection.

  • Size – The larger a SPN is, the more likely it is to be cancer.

  • Appearance of the SPN on x-ray – Pulmonary nodules that look round and smooth on x-ray are more likely to be benign, whereas those that appear irregular are more likely to be malignant.

More about the differences between benign and malignant nodules and masses:

What Happens After My Doctor Finds a Solitary Pulmonary Nodule?

After finding a SPN, the first thing your doctor will want to do is check to see if you have any old chest x-rays or CT scans that he or she can compare with your current tests. SPN's that have not changed in size for 2 years are considered benign, and do not require further follow-up. If you do not have any previous chest x-rays, or if the nodule appears to be growing, there are several options that may be considered. Some of these include:
  • Observation – If a SNP is most likely benign, following it with repeat x-rays/CT scans may be recommended.

  • Repeat scans – Whenever medical tests are done, there is the chance that the results are in error. Sometimes a shadow, or how you are positioned when an x-ray is done, makes it look like there is something there when there isn’t. Repeating the test to make sure a nodule is indeed present may be recommended.

  • Further tests – Combining the results of a chest x-ray or CT scan with another test, such as a PET scan, may help your physician understand whether a nodule is something of concern.

  • Biopsy – The only way to know conclusively if a SNP is benign or malignant is to get a sample of tissue that can be examined under a microscope. Depending upon the location of the SNP, options that may be recommended include bronchoscopy, fine needle aspiration biopsy (FNA), video-assisted thorascopic surgery (VATS) or a thoracotomy.


National Institute of Health. Solitary Pulmonary Nodule. 08/24/11. http://www.nlm.nih.gov/medlineplus/ency/article/000071.htm.

Soubani, A. The evaluation and management of the solitary pulmonary nodule. Postgraduate Medical Journal. 2008. 84(995):459-66.

van Westeinde, S. et al. How to deal with incidentally detected pulmonary nodules less than 10mm in size on CT in a healthy person. Lung Cancer. 2008. 60(2):151-9.

Wahidi, M. et al. Evidence for the treatment of patients with pulmonary nodules: when is it cancer?: ACCP evidence-based clinical practice guidelines (2nd edition). Chest. 2007. 132(3 Suppl):94S-107S.

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