Often lung cancer ends fatally. A major reason for this is that the tumour frequently is being detected at an advanced stage only. Furthermore, the effectiveness of modern therapies, such as the immune therapy, is limited as well. Scientists of the Max Planck Institute for Heart and Lung Research in Bad Nauheim and the Justus Liebig University in Giessen proved that a certain group of leukocytes, so-called tumour-associated macrophages, play an essential role during the formation of metastases. The hereby involved molecular regulatory cascade might be a target for future therapeutic measures.