Mets Basics

On this page, you can learn the basics about metastatic breast cancer, so you can begin to better understand this disease.


  • Definition: When breast cancer becomes metastatic, it has left the breast and surrounding local area and moved to other parts of the body.
  • Terminology: Doctors also call metastatic breast cancer “stage 4 (or “IV”) breast cancer, or “mets.” In addition, they may call it “advanced breast cancer,” though this term can also refer to some stage-3 cancers, which are not metastatic. Please see staging for more information.
  • Prevalence: Five-to-nine percent of women diagnosed with breast cancer for the first time are diagnosed with metastatic breast cancer.
  • Spread: When breast cancer spreads, it usually goes to the bones, liver, lungs or brain, though it can spread elsewhere. Even after traveling, these cells remain breast-cancer cells. Doctors still call this breast cancer and it responds best to breast cancer treatments.
  • Diagnosis: Doctors often suspect metastatic breast cancer because of a symptom – perhaps a recurring pain or cough, shortness of breath, lack of appetite, headaches or an injury. They can also identify possible metastases through routine scans. They cannot make an absolute diagnosis of metastatic breast cancer without a biopsy, however. Studies show, though, that finding metastases early does not help increase survival. It is important to not blame yourself for not finding your recurrence early if you missed a scan or test, or put off getting something checked for a little while.