Pulmonary Nodules

Ask the DOC

A pulmonary nodule is an abnormal area in the lung that is less than 3 cm (sl. over 1 inch) in size. Pulmonary nodules are often discovered by accident when a chest x-ray or chest computed tomography (CT) scan is performed for another reason (this is called an incidental finding). Approximately 50% of those who undergo CT screening for lung cancer are found to have a pulmonary nodule.

The good news is that about 95% of pulmonary nodules are benign (not caused by cancer). A benign solitary pulmonary nodule may be a residual scar from a previous lung infection caused by a fungus, tuberculosis, bacteria, or a parasite. Less frequently it may be caused by a current infection. Other causes include benign lung tumors, cysts, pulmonary blood vessel abnormalities, lung inflammation from rheumatoid arthritis or sarcoidosis, a mucus plug, or a contained pocket of fluid in the lung.

When a nodule is caused by cancer, the most common causes are lung cancer or a single metastasis (cancer spread from another location). The most common cancers associated with a pulmonary nodule are breast, head and neck, colon, kidney, skin (melanoma), or bones or soft tissue (sarcoma).

In addition to the causes of solitary pulmonary nodules, multiple pulmonary nodules may also be caused by prolonged exposure to coal dust or mineral dust (silica or beryllium) and blood clots mixed with bacteria that travel through the blood stream (known as infectious emboli, sometimes seen in heart valve infections [endocarditis]).

Multiple pulmonary nodules may also be caused by metastatic cancer. The risk that a pulmonary nodule may be cancerous rises with larger nodules, nodules with irregular borders, a more solid appearance on CT, and location in the upper parts of the lungs. Patient factors that may increase the likelihood of cancer include current or former cigarette smoking, older age, personal history of cancer, family history of lung cancer, emphysema (COPD), and exposure to asbestos or radon.

Anyone with a pulmonary nodule discovered on a chest x-ray should have a chest CT. In addition, if chest x-rays or CTs were done in the past, comparison of the current results to the previous exams will reveal whether the nodule is a new or pre-existing finding, or whether a pre-existing nodule has grown in size. Then, depending on the patient risk factors and the characteristics of the nodule, an individualized plan should be developed in consultation with a physician, often a pulmonologist, who is familiar with current guidelines regarding the management of pulmonary nodules.

Nodules deemed to be at low risk can be followed with CT scans at designated intervals. If a nodule remains stable over a two year period, they are generally considered to be benign. Nodules at intermediate or high risk of being cancerous should be further evaluated, which may include a positron emission tomography (PET) scan, biopsy, and/or surgery.

For more information go to the American Thoracic Society at:


Please direct questions and comments to This email address is being protected from spambots. You need JavaScript enabled to view it.

 By Peter Galvin, MG

Sign up via our free email subscription service to receive notifications when new information is available.