Pulmonary nodules are abnormalities in the lungs. They can be found during CT screening for lung cancer, but can also be found incidentally on imaging completed for an unrelated reason (like after a fall or car accident). Pulmonary nodules can be single (one) and are referred to as solitary pulmonary nodules. They can also be numerous (many). Sometimes pulmonary nodules can grow, and other times they can remain the same size or go away completely. They can be solid, part solid, or ground glass in appearance. Nodules can be related to lung cancer, but can also reflect prior trauma, infections, and some more rare systemic diseases. Nodules can also be related to cancer spread from other sites of disease (metastatic lesions).
Solitary Pulmonary Nodules are defined as solitary nodules < or equal to 30 mm in size, fully surrounded by aerated lung, without other features (no atelectasis, pleural effusions or enlarged lymph nodes). The risk of malignancy in a solitary pulmonary nodule depends on several factors. First, the risk of malignancy (cancer) is related to the size of the nodule. Smaller nodules have a lower risk of being cancers, but often still need imaging follow up to ensure that they do not grow over time. If a nodule is <5 mm, there is a <1% risk of malignancy, between 5 mm and 10 mm, that risk increases to 6-28%. For nodules over 20 mm, the risk of malignancy is 64-82%.
Size is not the only criteria to determine a nodule’s risk of malignancy. If a nodule remains the same size for two years on imaging, the nodule is thought to be low risk for cancer. Nodules with calcification are also more likely to be benign (non-cancerous). Nodules located in the upper lobes of lungs, and those found in smokers or on lung cancer screening exams are higher risk for malignancy. Nodules that grow over time are also higher risk for malignancy.
The Fleischner Society is an international multidisciplinary society founded in 1969 to develop consensus guidelines for chest imaging. These guidelines are used by chest physicians (thoracic surgeons and pulmonary medicine) to develop treatment plans for patients with pulmonary nodules, based on the size and characteristics of the nodule, as well as the patient’s underlying risk factors (age, smoking history). Pulmonary nodules may be observed with serial imaging (CT scan) studies in some cases. Other patients with pulmonary nodules may require a needle biopsy and/or surgery for diagnosis and definitive treatment.