A tumour occurs in the liver as a result of the uncontrolled reproduction of damaged cells. The tumour robs normal, healthy cells of oxygen and nutrients. Metastatic tumours (tumours that spread from one location in the body to another) occur when large tumors shed tumor cells which can grow and function apart from the primary tumor. Metastatic tumor cells move throughout the body via the circulatory or the lymphatic system. Because the liver is near or connected to several significant organs, metastatic liver cancer affects over 75% of all terminal cancer patients.