Detailed Guide: Bone Metastasis

March 22, 2007 — -- Metastatic cancer is cancer that has spread from the part of the body where it started (called 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.

When the cells travel through lymphatic channels they can become trapped in lymph nodes, often those closest to the cancer's primary site. When the cells travel through the bloodstream they can go to any part of the body. Most of these cells die, but occasionally they don't. They 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 breast cancer. A person with breast cancer that has spread to the bones is said to have breast cancer with bone metastases.

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:

Sometimes the metastatic tumors have already developed when the cancer is first diagnosed. In some cases, this metastasis is discovered before the primary (original) tumor is found. Sometimes a cancer can spread widely throughout the body before it is discovered without developing as a large tumor in the site where it started. When the original site cannot be determined, this condition is called cancer of unknown primary, and is discussed further in a separate American Cancer Society document.