Figure 5b. Lung cancer: Pancoast tumor in a 57-year-old man. Oblique sagittal T1- (a) and T2-weighted (b) images and axial T2-weighted image (c) show a large right apical lung mass that invades and encases the roots of the right brachial plexus. The subclavian vessels and cords of the brachial plexus are not identifiable. The mass has an irregular interface (arrows in a) with the adjacent lung parenchyma. This mass was proved at biopsy to be a non-small cell lung cancer.