These scenarios represent opposite ends of the continuum of favourable to adverse factors for survival after resection of pulmonary metastases. Most patients operated on fall between these extremes and it is evident that if there is a "yes" towards one end of the continuum and "no" towards the other that there must be cross over zone where there is clinical uncertainty. PulMiCC aims to investigate the outcome following pulmonary metastasectomy in patients where there is accepted clinical uncertainty, to provide evidence to guide practice in the future.