Most types of cancer are classed as belonging to stages 0, I, II, III or IV. The stage assigned to the cancer refers to the extent of its spread at the time of diagnosis. According to Cancer.Net, which stage a cancer is at determines the recommended course of treatment and the likely prognosis for the patient.
Stage 0 cancers are confined to the immediate area where the abnormal growth began. At this stage, according to Cancer.Net, most cancers are highly curable and have not begun to spread into surrounding tissues. Stage I cancers have begun to spread, but they are still confined to the original tissues where the cancer began. A cancerous growth is said to have achieved Stage II when it breaks through the membrane covering the affected tissues. This is a critical development, as it indicates that the cancer is likely to spread throughout the body and cause serious, and possibly fatal, damage. At stage II, the cancerous cells may have spread into the lymph nodes closest to the site of the original growth. Stage III cancers have grown large, and they are often detectable throughout the lymphatic system. At stage IV, cancer is present throughout the body. In general, the higher the stage at which cancer is detected, the worse the prognosis for the patient becomes.