The main stages of breast cancer include Stage 0 where the cancer is only within the ducts, Stage I where the tumor is small and may or may not have spread to the local lymph nodes, Stage II where the tumor is between 2-5cm and may or may not have spread to the regional lymph nodes, Stage III where the tumor has spread to more than 4 lymph nodes or is larger than 5cm, and Stage IV where the tumor has spread to other parts of the body.