1) 90o contact with the aorta; 3) fat visible between the mass and mediastinal structures. Importantly however, this information does not identify inoperable tumours (thus avoiding unnecessary thoracotomy) because ~50% of the technically resectable tumours had >3 cm of mediastinal contact or loss of the clear fat plane. Artificial pneumothoraces have been used to improve detection of both mediastinal and chest wall invasion by examining whether or not the pleura peels away from the relevant structure. Although one study demonstrated 100% accuracy for chest wall invasion, its accuracy for mediastinal involvement was only 76% [96]. Another study was 100% sensitive for mediastinal and chest wall invasion but only 80% specific [97]. This again indicated that the technique cannot be categorical about the presence of unresectability.