Purpose: To retrospectively assess the usefulness of contrast-enhanced computed tomographic (CT) attenuation measurements for differentiating renal cell carcinoma pulmonary metastasis from primary lung cancer.
Methods: The authors retrospectively evaluated 39 pulmonary nodules in 36 patients with pulmonary metastasis from renal cell carcinoma (RCC; 29 men and 7 women; mean age +/- SD, 56.9 +/-10.0 years; range, 38-76 years) and 30 pulmonary nodules in 42 patients with primary lung cancer (33 men and 9 women; mean age +/- SD, 62.9 +/- 9.8 years; range, 38-81 years). Contrast-enhanced scans were obtained 35 seconds after injecting contrast medium intravenously. Pulmonary nodules were retrospectively analyzed by determining nodule attenuation values in contrast-enhanced CT scans. The Mann-Whitney U test was used to compare pulmonary nodule mean attenuation values in these 2 patient groups.
Results: The mean attenuation value of metastatic pulmonary nodules from RCC (mean +/- SD, 73.6 +/- 40.6 Hounsfield units) was greater than that of primary lung cancer nodules (mean +/- SD, 47.8 +/-17.9 Hounsfield units) (P < 0.001).
Conclusions: Pulmonary nodule attenuation measurements obtained by contrast-enhanced CT are useful for differentiating pulmonary metastasis from RCC and primary lung cancer.