Understanding Metastatic Cancer
For patients and caregivers
Metastatic cancer has spread from the part of the body where it started (its primary site) to other parts of the body. When cells break away from a cancerous tumor, they can travel to other areas of the body through either the bloodstream or lymphatic channels.
If the cells travel through lymphatic channels they can become trapped in lymph nodes that are usually near the cancer. If the cells travel through the bloodstream they can go to any part of the body. Most often, the cancer cells break off and travel in the bloodstream. Most of these cells die, but occasionally they don't and settle in a new location, begin to grow, and form new tumors. The spread of a cancer to a new part of the body is called metastasis.
Even when cancer has spread to a new location, it is still named after the part of the body where it started. For example, if prostate cancer spreads to the bones, it is still called prostate cancer, and if breast cancer spreads to the lungs it is still called breast cancer. When cancer comes back in a patient who appeared to be free of cancer (in remission) after treatment, it is called a recurrence. Cancer may recur as:
- local recurrence (in or near the same organ it developed in);
- regional recurrence (in nearby lymph nodes or in the area that lymph nodes had been removed from); or
- distant recurrence, involving any other part of the body not included in local or regional recurrence.
Distant recurrence is also called metastatic recurrence. For example, the cancer might recur in distant parts of body, such as in bones, the liver, or the lungs. This happens because some cancer cells have broken off from the original tumor, traveled elsewhere, and begun growing in these new places.
Sometimes the metastatic tumors have already begun to grow when the cancer is first diagnosed. In some cases, a metastasis may be discovered before the primary (original) tumor is found. If a cancer has spread widely throughout the body before it is discovered, it may be impossible to determine exactly where it started. This condition is called cancer of unknown primary.
One example of cancer of the unknown primary would be a person with an enlarged lymph node on the side of the neck. When it is removed, it is found to contain cancer. But the appearance of the cancer under the microscope does not look like a cancer that starts in lymph nodes. At that point it might be called cancer of unknown primary. Often, though, its appearance might suggest that the cancer started in the mouth, throat, or voice box (larynx). During a thorough exam of this area, a small cancer of the pharynx might be found. From then on, the patient is said to have pharyngeal cancer rather than cancer of unknown primary and will receive treatment that is appropriate for that cancer. Similarly, if a cancer is found to have started in the lung, breast, or other organ, it is no longer considered a cancer of unknown primary origin.
Link to Glossary
For more comprehensive information about metastatic cancer, patients should talk with their doctor and healthcare team. Additional information can also be found at the following sites:
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