Pulmonary Metastases

Abstract

Pulmonary metastases represent spread of malignancy to the lung parenchyma. Patients with metastatic disease may present with dyspnea, cough, or hemoptysis. Alternatively, affected patients may be asymptomatic. The lungs are a common site for metastatic disease. Relatively common primary malignancies (breast, colon, lung, and kidney cancers) are the most common causes of pulmonary metastases. However, less common primary malignancies (choriocarcinoma, testicular cancers, melanoma, and sarcomas) have a higher likelihood to produce lung metastases. The vast majority of pulmonary metastases spread via the bloodstream. Hematogenous metastases are typically basilar predominant lung nodules. Metastatic nodules may be very small (miliary, < 3mm), or very large (cannonball), and may rarely be solitary. The presence of surrounding ground-glass attenuation (CT-Halo sign) often indicates surrounding hemorrhage. Some metastases may be cavitary or calcified. Pulmonary metastases may spread via the lymphatics. Asymmetric smooth or nodular interlobular septal thickening should raise concern for lymphangitic carcinomatosis. An uncommon mechanism is spread within the airways, which may result in an endobronchial lesion or post obstructive atelectasis.