Pulmonary Nodule
A pulmonary nodule is a small, rounded area of abnormal tissue in the lung, generally less than about 3 centimeters in size. (Larger areas are called lung masses.) Pulmonary nodules are very common and are most often discovered incidentally on chest CT or X-ray performed for other reasons. The majority are benign—caused by old infections, scars, or harmless growths—but some can represent early lung cancer or metastasis from another tumor. Careful evaluation of the nodule’s size, shape, and other features helps determine whether further testing or follow-up is needed.
What is it?
A pulmonary nodule is a small, rounded spot in the lung that measures less than about 3 centimeters across on imaging. Larger lesions (over 3 cm) are referred to as lung masses. Pulmonary nodules are sometimes called “coin lesions” because of their rounded shape. They can be solid, partially solid, or appear as a hazy area called ground-glass opacity—each pattern having somewhat different clinical implications.
Pulmonary nodules can develop for many reasons. The most common causes are benign and include healed infections (such as old tuberculosis or fungal infections), small scars, granulomas, benign tumors such as hamartomas, and inflammation-related findings. Less commonly, a nodule may represent early-stage lung cancer or a metastasis from a tumor elsewhere in the body. Risk factors that raise the likelihood of malignancy include current or prior smoking, increasing age, a family history of lung cancer, prior cancer, exposure to asbestos or radon, and certain occupational or environmental exposures. Imaging features that influence assessment include the nodule’s size, growth over time, shape (smooth versus irregular or spiculated margins), density, presence of calcification, and location.
The great majority of pulmonary nodules cause no symptoms and are found incidentally on chest X-rays or CT scans performed for other reasons (such as evaluation of chest pain, shortness of breath, or before unrelated surgery), or on lung cancer screening CT. When symptoms occur, they more often relate to an underlying condition than to the nodule itself—for example, cough, fever, or chest pain from a pneumonia that leaves behind a residual nodule.
CT of the chest is the primary imaging test for evaluating a pulmonary nodule because it provides detailed information about size, shape, density, and other features. The radiologist’s report typically describes these features and often suggests a follow-up plan based on widely used guidelines (such as Fleischner Society recommendations) that take into account the size of the nodule, its appearance, and the patient’s individual risk for lung cancer. Common next steps include short-interval follow-up CT to look for change, PET/CT to evaluate metabolic activity, image-guided or bronchoscopic biopsy, or, in some cases, direct surgical removal. Many nodules can simply be observed with serial CT scans, and stability over time strongly suggests a benign cause.
Important to Know
Most pulmonary nodules are benign, and even when follow-up is recommended, the goal is typically to confirm stability or catch any change early rather than to indicate that cancer is likely. Recommendations for follow-up depend on the size and characteristics of the nodule, the type of nodule (solid, part-solid, or ground-glass), and the patient’s overall risk. Smokers, former smokers, and people with other risk factors generally have closer surveillance than low-risk patients.
When imaging features are suspicious—such as larger size, irregular or spiculated margins, growth over time, or high metabolic activity on PET—further evaluation with biopsy or surgical removal may be recommended. When a nodule is confirmed to be cancer, treatment depends on the type and stage and may include surgery, radiation, chemotherapy, immunotherapy, or targeted therapy. When a nodule is confidently identified as benign (for example, a typical hamartoma or a fully calcified granuloma), no further evaluation may be needed.
Decisions about whether to observe, biopsy, or treat a pulmonary nodule are typically made in collaboration with primary care physicians, pulmonologists, thoracic surgeons, interventional radiologists, and oncologists, with imaging findings interpreted alongside the patient’s overall medical history and preferences.
Red flag symptoms include coughing up blood, persistent or worsening cough, unintended weight loss, significant fatigue, severe or worsening shortness of breath, chest pain, or new neurological symptoms in someone with a known nodule and risk factors for lung cancer. These warrant prompt medical evaluation.