Tests and scancs to work out what stage a cancer is – how large it is and whether it has spread. For most cancers there are four stages. Stage one is a small localised cancer. Stage four is a cancer that has spread away from where it started to another body organ. TNM is a more detailed staging system used by doctors. It describes the size of the tumour (T), whether there are lymph nodes containing cancer cells (N), and whether the cancer has spread (M).