When a cancer spreads (metastasizes) from its original site to another area of the body, it is termed metastatic cancer. Virtually all cancers have the potential to spread this way. Whether metastases do develop depends on the complex interaction of many tumor cell factors, most of which are not completely understood.
The treatment of metastatic cancer depends on where the cancer started. When breast cancer spreads to the lungs, for example, it remains a breast cancer and the treatment is determined by the tumor's origin within the breast, not by the fact that it is now in the lung. About 5 percent of the time, metastases are discovered but the primary tumor cannot be identified. The treatment of these metastases is dictated by their location rather than their origin ( see "Cancer of an Unknown Primary Site" ).
Although the presence of metastases generally implies a poor prognosis , some metastatic cancers can be cured with conventional therapy.
Types Virtually all cancers can develop metastases.
