A primary cancer is where the cancer originally started. Sometimes cancer cells break off from this primary and spread to other parts of the body. These are called secondary cancers or metastases. This means for example, that if someone has primary breast cancer i.e. a cancer that has started in the breast, which has spread to the bones, these are bone secondaries and will be made up of breast cancer cells. A primary bone cancer i.e. a cancer which has started in the bones, will be made up of bone cancer cells. Cancers are treated according to where they started. If you are unsure whether your cancer is primary or secondary please clarify this with your doctor or nurse. Alternatively contact the Cancerbackup information service on 0808 800 1234 (UK Only)