This document outlines the staging system for breast cancer according to the American Joint Committee on Cancer's 7th edition. It divides breast cancer into 5 main stages (0-IV) based on the size and spread of the primary tumor (T), whether the cancer has spread to the lymph nodes (N), and whether there is distant metastasis (M). Each stage is then broken down into smaller subgroups to further characterize the cancer's progression. The document also defines terms used in the TNM classification system.