A lung nodule, also called a pulmonary nodule, is one of the most common abnormalities seen on radiographic images, and is a small mass of tissue in the lung that is smaller than 3 cm (slightly more than an inch) in diameter. The nodule appears as a white shadow on a chest X-ray or computerized tomography (CT) scan. Generally, a pulmonary nodule must grow to at least 1 cm (size of a pea) in diameter before it can be seen on a chest X-ray. CT scans can detect much smaller nodules.
Most lung nodules are benign (noncancerous) and may be due to a previous infection in the lung or other cause; however, they may represent an early stage of primary lung cancer or they may indicate that cancer is spreading from another part of the body to the affected lung.
Because chest X-rays and CT scans help to identify such a wide variety of lung disorders, lung nodules must be thoroughly evaluated, diagnosed and treated appropriately. Even if the nodule presents no current threat, it must be regularly monitored for any change.
Persons with a lung nodule or nodules do not experience any symptoms, and they are usually noticed by chance on a chest X-ray or CT scan taken for another reason (referred to as an incidental finding).