Nodules, lung

Synonyms: Pulmonary nodules

Medical Specialties: Internal medicine, Oncology, Pulmonology

Clinical Definition

A lung nodule is a rounded opacity surrounded by lung parenchyma. It is equal to or less than 3 centimeters in diameter and usually well marginated. Lung nodules may be benign tumors, such as a hamartoma or a malignancy. Growths larger than 3 centimeters are generally classified as masses and suspected to be malignancies until otherwise proven.  

In Our Own Words

A lung nodule is a small, round growth on the lung that is less than 3 centimeters in diameter. Growths larger than 3 centimeters are usually classified differently and are considered masses. A lung nodule may sometimes be referred to as a spot on the lung. It may be an “incidental finding” on a chest X-ray or CT scan; meaning the scan was done for a different reason, but a nodule was detected when the radiologist reviewed the image.


Although a nodule or spot on the lung sounds serious and can be cancerous, it can also have several other causes that are not cancer. Lung nodules can develop as a result of past infections and scar tissue formation. Certain disorders, such as rheumatoid arthritis and sarcoidosis, can also cause lung nodules. 

Relevant Conditions
Common Types
  • Solitary or multiple
  • Infectious, benign or cancerous
Share this article
  • Girvin F., Ko J. “Pulmonary Nodules: Detection, Assessment, and CAD.” American Journal of Roentgenlogy. 2008; 191(4). Accessed September 2013.
  • University of Maryland Medical Center. “Solitary pulmonary nodule.” Updated May 2013. Accessed September 2013.
  • Cleveland Clinic. “Pulmonary Nodules.” Accessed September 2013.
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