When a cancer starts growing in one part of the body we call this the primary cancer. Sometimes cancers can spread from this primary site into other parts of the body and we call this secondary or metastatic cancer. Normally the primary cancer grows the quickest and is the first to cause problems. But sometimes secondary cancers are found in one or more parts of the body and there is no obvious primary cancer. If we have been unable to find your primary cancer we refer to this as cancer of unknown primary.