Solitary pulmonary nodule

A solitary pulmonary nodule (SPN) is an abnormal growth in the lung. Often a person who has an SPN does not have any respiratory symptoms. A chest X-ray done for some other reason usually detects an SPN.

An SPN found on a chest X-ray does not mean lung cancer is present. A past lung infection can cause a noncancerous SPN to develop. However, of all SPNs doctors think might be cancer and have tested with a biopsy, about 40% to 60% are cancerous.1 Noncancerous SPNs often are caused by a previous infection in the lung. Further tests can be done to determine whether the SPN is noncancerous (benign) or cancerous (malignant).

A CT scan normally is done to help determine the growth rate, the shape of the nodule, and the pattern of calcification in the nodule to help identify whether it is cancerous. Positron emission tomography (PET) scans are being studied to determine whether they can help distinguish between noncancerous and cancerous SPNs.

In general, the larger the SPN, the more likely it is to be cancerous. A very small SPN has less than a 1% chance of being cancerous. The risk increases to 80% for a large SPN.2

Your health professional may use a probability of cancer (PCA) table to help determine the risk that an SPN is cancerous. Then he or she may recommend follow-up testing with a biopsy or regular CT scans or, if it is very likely the SPN is cancerous, the doctor may suggest determining its stage and removing it with surgery.2

The following table shows when solitary pulmonary nodule is likely or not likely to be cancer. None of these are true in every case, but these factors are used to help decide whether further testing or treatment is needed.1

Solitary pulmonary nodule: Is it likely to be cancer?
It's probably not cancer It's probably cancer
  • You are younger than 35.
  • The nodule is smaller than 2 cm (0.8 in.).
  • The nodule edge is smooth and regular.
  • You have never smoked.
  • The nodule has thick areas (calcifications).
  • You have a history of rheumatoid arthritis.
  • You have a history of exposure to tuberculosis (TB) or a fungal infection.
  • The nodule either grows very quickly, or does not grow much over 2 years.
  • You are older than 50.
  • The nodule is bigger than 3 cm (1.2 in.).
  • The nodule edge is irregular or jagged.
  • You are a smoker. The more you have smoked, the more likely the SPN is to be cancer.
  • The nodule does not have thick areas.
  • You have a history of exposure to asbestos, radiation, or radon.
  • You have a history of COPD.
  • The nodule grows bigger at a moderate, steady rate.

A transthoracic needle aspiration (TTNA), which uses a long needle inserted through the chest wall, can sometimes be used to remove a tissue sample from an SPN. This usually is done if the abnormal lung tissue is located close to the chest wall. Imaging procedures such as CT scan, ultrasound, or fluoroscopy usually are used to help guide the needle to the right spot. Another possible test is bronchoscopy with transbronchial biopsy (TBB). In this test, a flexible tube is inserted through the nose and down to the lungs. A camera in the tube shows where the SPN is, and a tiny tool in the same tube takes a small sample of the SPN tissue.

Most cancerous nodules can be identified through biopsy, but positive identification of noncancerous nodules can still be difficult. If a biopsy shows cancer, surgery can often remove the cancer. If your doctor determines that you have a high risk of having a cancerous nodule, he or she may decide not to do this test and instead recommend surgery to remove the nodule. A pathologist looks at the nodule under a microscope to see if it is cancer.

Follow-up testing for a noncancerous SPN includes chest X-rays or CT scans as often as your doctor recommends to look for any change in the size or shape of the nodule.2


  1. Kruklitis RJ, et al. (2004). Solitary pulmonary nodule and lung tumors other than bronchogenic carcinoma. In JD Crapo et al., eds., Baum's Textbook of Pulmonary Diseases, 7th ed., pp. 859–862. Philadelphia: Lippincott Williams and Wilkins.
  2. Chesnutt MS, et al. (2008). Pulmonary disorders. In SJ McPhee et al., eds., Current Medical Diagnosis and Treatment, 47th ed., pp. 203–243. New York: McGraw-Hill.

Last Updated: June 4, 2008

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