The stages of breast cancer

The stages of breast cancer are indicated using Roman numerals ranging from 0 to IV, with 0 indicating cancer that is noninvasive or contained within the milk ducts. Greater numerals indicate a more invasive cancer. By stage IV breast cancer, also called metastatic breast cancer, the cancer has spread to other areas of the body.

The cancer staging system continues to evolve and is becoming more complex as doctors improve cancer diagnosis and treatment.