The ability of tumour cells to detach themselves from a cell group, penetrate the bloodstream or lymphatic system, settle in other organs and continue to grow there is a unique and typical characteristic of malignant tumours. We call such daughter tumours, which grow far away from the primary tumour, metastases. The destructive, invasive growth of malignant tumors, the loss of cell function and the ability to metastasize usually lead to a serious disease with accompanying symptoms and usually result in death if adequate treatment is not provided.