Tumor staging is a process used to determine the extent and severity of cancer in a patient's body. It helps doctors understand how far the cancer has spread, which is crucial for planning treatment. Staging typically involves imaging tests, biopsies, and physical examinations to assess the size of the tumor and whether it has affected nearby lymph nodes or other organs. The most common staging system is the TNM system, which stands for Tumor, Node, and Metastasis. In this system, the size of the primary tumor is measured (T), the involvement of regional lymph nodes is evaluated (N), and the presence of distant metastasis is checked (M). This information guides treatment decisions and helps predict patient outcomes.