The evaluation and management of the solitary pulmonary nodule

Solitary pulmonary nodules (SPNs) are increasingly detected with the widespread use of chest computed tomography (CT) scans. The primary goal of the evaluation of these nodules is to determine whether they are malignant or benign. Clinical factors such as older age, tobacco smoking and current or remote history of malignancy increase the pre-test likelihood of malignancy. Radiological features of the SPN based on chest CT with high resolution cuts are critical in differentiating between benign or malignant lesions. These features include size, change in size, the presence and pattern of calcification, edge characteristics, attenuation, and contrast enhancement. SPNs that are stable in size for > 2 years and those with benign pattern of calcification do not need further studies. Lesions with clear change in size are malignant until proven otherwise and require tissue diagnosis. Frequently, the aetiology of the SPN following chest CT scan remains indeterminate and requires further evaluation. The approach to the management of indeterminate SPN ranges between observation with repeat chest CT scan, further diagnostic studies such as positron emission tomography (PET) scan, or invasive procedures to obtain tissue diagnosis. These procedures include bronchoscopy, transthoracic needle aspirate, and resection by video assisted thoracoscopy or thoracotomy. Determination of which approach to follow depends on the pre-test probability of malignancy, whether the patient is a surgical candidate, and the patient's informed preferences. This article reviews the radiological features of the SPN and their value in differentiating between benign and malignant lesions. This is followed by discussion of the different approaches to the management of the SPN after initial characterisation by chest CT scan, including the benefits and limitations of the different diagnostic studies.