Pulmonary metastases: Vascular supply and diagnosis

Abstract

Pulmonary metastases may exhibit a very broad spectrum of appearances; they may range from widespread micronodular iniiltration of the lung through multiple, discreet, sharply defined spherical lesions, to single, solid or cavitating lesions of minute to massive size. As a result, there is a wide range of differential diagnoses and no absolutely characteristic roentgen pattern by which the diagnosis of pulmonary metastasis can be made with complete confidence.2 However, the possible differential diagnoses become very few in number when one sees the classic pattern of multiple sharply defined spherical lesions, without surrounding parenchymal reaction, increasing in size over a period of time. With the advent of angiography, particularly with super selective techniques, it was hoped that characteristic circulatory differences might serve to distinguish benign from malignant lesions and metastatic deposits from primary tumors.4s*‘0 Many authors believe that all pulmonary malignancies, whether primary or secondary, are supplied purely by the bronchial circulation; several papers on the vascular pattern of metastases and the uses of angiography in diagnosing pulmonary malignancies are based on this premise.3*‘o However, we have shown both by analysis of clinical case material (post mortem and in viva ) and by the use of experimental animal models, that vascularization of pulmonary malignancies is not confined to the bronchial circulation.lJ” While most primary malignancies do have a predominantly bronchial circulation, they often have a pulmonary component (Fig. 1).5 Most metastases have a pulmonary circulation; however, this depends to some extent on their position in the lung. Metastases within the perihilar region usually take a bronchial arterial supply, and those in the outer two thirds of the lungs take a pulmonary supply.6 It is widely believed that adult pulmonary arteries cannot proliferate any further (i.e. cannot produce neovascularity); but our examination of both clinical and animal experimental material clearly demonstrated pulmonary neovascularity in metastatic deposits from primary lesions of a widely differing histology (Fig. 2). In the clinical material