A solitary pulmonary nodule is defined as a relatively round lesion that is <3 cm in diameter and completely surrounded by lung parenchyma. It is distinct from lung lesions >3 cm in diameter, which are considered lung masses. Traditionally, the definition of solitary pulmonary nodule has also excluded a ground-glass infiltrate seen on CT scan, as this finding is commonly associated with bronchioalveolar cell carcinoma and does not fulfil the physical characteristics of a nodule.  For the purposes of this monograph, we will consider ground-glass opacities as solitary pulmonary nodules.
The goals in managing a patient with a solitary pulmonary nodule are to distinguish the benign from the malignant nodule and, when malignancy is either confirmed or strongly suspected, to expedite resection.
For solitary pulmonary nodules, established clinical features (e.g., patient age, smoking status) and radiographic findings (e.g., calcification, growth rate, size) help determine a probability of malignancy. If necessary, non-invasive and/or invasive testing is used to more accurately determine the probability of malignancy to a level that enables a decision to be made regarding observation or resection. Therefore, the proper use of these tests mandates knowledge about their performance characteristics. Decision analysis approaches using Bayesian methods may also assist with the calculation of the probability of malignancy, although these methods have not consistently outperformed the clinical assessment and testing approach.