Indeterminate Pulmonary Lesion
An indeterminate pulmonary lesion is a spot or abnormal area seen on imaging that cannot be confidently labeled as benign (non-cancerous) or malignant (cancerous) based on that single study alone. These lesions are often found incidentally during imaging performed for unrelated reasons, such as a cough, infection, or lung screening. Many ultimately prove to be benign, but careful follow-up is essential to ensure that no concerning changes develop over time.
What is it?
An indeterminate pulmonary lesion is a general term for an area in the lung that appears abnormal on imaging but does not have enough specific features to determine what it represents immediately. These lesions may appear as small nodules, hazy areas, or more solid spots that could reflect infection, inflammation, scarring, or—less commonly—an early cancer. Because several different conditions can look similar on a single scan, the lesion remains “indeterminate” until more information is gathered.
Radiologists carefully evaluate the lesion’s size, shape, edges, density, and location to assess the likelihood that it is benign or malignant. They also compare with prior imaging to determine whether the lesion is stable, new, or changing. In many cases, the best approach is to repeat imaging after an appropriate interval to see whether the lesion grows, shrinks, resolves, or remains stable.
Important to Know
Most small (typically <8 mm) indeterminate lung lesions, especially in people without major risk factors, turn out to be benign findings such as prior infection or scarring. However, certain features—including spiculated or irregular borders, rapid interval growth, or enlarged nearby lymph nodes—can raise concern and may require more urgent evaluation. CT imaging plays a central role, and radiologists follow established guidelines to determine the appropriate timing of follow-up scans.
Additional testing may include PET/CT, which assesses metabolic activity, or a biopsy to obtain tissue for diagnosis when needed. Red flag symptoms that should be discussed with a healthcare provider include persistent cough, coughing up blood, unexplained weight loss, new or worsening shortness of breath, or chest pain. Following recommended imaging and evaluation pathways helps ensure early detection of concerning lesions while avoiding unnecessary procedures for benign ones.