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A lung nodule is a small area found in the lung, often during an imaging test such as an x-ray or CT scan. It is sometimes called a “spot on the lung” or a “shadow.”
Most lung nodules are very small, less than 10 mm in diameter. On imaging tests, they are round areas that are solid or look like they are filled with fluid. Because they are so small, lung nodules don’t cause any signs or symptoms.
Lung nodules are caused by scar tissue, old infections, inflammation or breathing in harmful substances like tobacco, asbestos or radon. Some people might develop lung nodules without any identified cause.
Almost all lung nodules are non-cancerous (benign). But sometimes a lung nodule is cancer. There is a higher risk that a lung nodule is cancer in older people who have smoked or still smoke or who have other risk factors for lung cancer, such as exposure to asbestos. Lung nodules that are larger than 8 mm are more likely to be cancer.
Next steps if you have a lung nodule
Many people who have a lung imaging test will have a lung nodule or nodules found in their lungs. Most people with lung nodules do not need to have a lung biopsy.
If you are diagnosed with a lung nodule, your healthcare team may look at any older imaging tests that you have had of your lungs.
For larger lung nodules, you may need to have another CT scan to see if the nodule grows or changes.
If the lung nodule does not grow or change over time, it is likely not lung cancer. Your healthcare team may stop doing the imaging tests if a lung nodule has not changed after 2 years of watching. Most lung nodules do not change over time.
If the lung nodule grows or changes, you may need to have other imaging tests or a lung biopsy. Most lung cancers grow very slowly. If the nodule has changed on your next imaging test, it will still be very small and treatable.
If the lung nodule is larger than 10 mm or has an irregular shape, your healthcare team may recommend a lung biopsy instead of monitoring you with imaging tests.