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 develop depends on the complex interaction of many tumor cell factors, including the type of cancer, the degree of maturity (differentiation) of the tumor cells, the location and how long the cancer has been present, as well as other incompletely understood factors.
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
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.
How It Spreads
Metastases spread in three ways - by local extension from the tumor to the surrounding tissues, through the bloodstream to distant sites or through the lymphatic system to neighboring or distant lymph nodes. Each kind of cancer may have a typical route of spread.
What Causes It
The characteristics of each tumor are different, and it is not known what factors make the metastasis develop in particular places.
Common Signs and Symptoms
Many patients have no or minimal symptoms related to the tumor and their metastases are found during a routine medical evaluation. If there are symptoms, they depend on the site involved.
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