The significance of pulmonary nodules detected by CT but not by chest radiography in tumour staging.

Computed tomography (CT) is more sensitive than the chest radiograph in the detection of pulmonary metastases, but specificity is lower because CT detects more small benign nodules. This study assessed the significance of pulmonary nodules demonstrated on CT when the chest radiograph was normal. Staging CT scans of 146 patients with extrathoracic primary tumours were reviewed. Thirteen per cent of CT scans showed pulmonary nodules despite a normal chest radiograph. In over 80% of these cases the nodules were benign. This has implications for accurate staging. When such nodules are demonstrated on CT, comparison with a repeat scan at a suitable interval will increase diagnostic confidence.