Cancer staging is a process used by healthcare providers to determine the extent of a person's cancer and help guide treatment decisions. It involves evaluating the size of the tumor, whether it has spread to nearby lymph nodes, and if it has metastasized to other parts of the body. Staging is important because it helps doctors understand how advanced the cancer is, predict prognosis, and develop an appropriate treatment plan. Staging systems vary depending on the type of cancer, but commonly use a combination of physical exams, imaging tests, and biopsies to assess the cancer's stage.