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Causes of Spots on Lungs

author image Dr. Ann M. Hester
Dr. Ann M. Hester is a board-certified internal medicine specialist and author. She is also the creator of the Patient Whiz patient engagement app for iOS and Total en Salud health app in Spanish.
Causes of Spots on Lungs
Doctor exams xrays of lungs of a adult Photo Credit Spencer Platt/Getty Images News/Getty Images

Occasionally, a chest x-ray or CT scan may reveal an unexpected abnormality in the lung. Doctors may use terms like spot, lesion, mass or nodule to describe these abnormalities in the lungs. While cancer is a possibility that everyone fears, most of these lung spots are due to other causes, such as infections, noncancerous growths or even blood vessel abnormalities.


Infections are one of the most common causes of spots on the lungs, though not necessarily an active infection. Granulomas are small areas of inflammation found in tissue -- frequently the lung tissue. While often due to a past infection, they may be seen with an active infection or certain noninfectious conditions. Some infections that may cause granulomas include tuberculosis and certain fungal infections. Sarcoidosis -- a disease of unknown cause that has the potential to cause granuloma formation in multiple organs -- is one of the most common noninfectious reasons for lung granulomas.

Noncancerous Growths

There are a variety of noncancerous causes of spots on the lungs. Hamartomas are disorganized collections of tissue that can be found in many different parts of the body. They typically cause no significant symptoms and are often incidentally picked up on imaging studies done for unrelated reasons. Lipomas are collections of fat cells that grow inside a capsule. Fibromas consist of tissue that contains fibers, such as connective tissue, which can also be found in various locations in the body. Hamartomas, lipomas and fibromas account for most noncancerous growths found in the lungs.

Cancerous Growths

Whether a tumor originates in the lung or spreads there from another location in the body, cancer is the most serious and potentially life-threatening cause of spots on the lungs. The implications for treatment and survival when cancer is found in the lungs run the gamut. A single, small cancer that originated in the lung and has not yet spread elsewhere may be very treatable. Multiple, large growths in both lungs that represent the spread of cancer from another site in the body are more difficult to treat.

Other Causes of Lung Spots

A variety of conditions may cause spots on the lungs, such as blood vessel abnormalities and rheumatoid arthritis. Some are harmless while others can be potentially life-threatening. Fortunately, radiologists frequently comment on the appearance of the lung spots, which helps the treating doctor make decisions about whether to pursue a workup of the abnormality. At times the lung spot is clearly due to an insignificant condition and there is no need to look further. However, at other times, the doctor may need to delve further, to be safe.

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