Metastasis
From ArticleWorld
A tumor is an abnormal tissue growth and may be either benign; in which case it usually stays in one place and dealt with surgically; or malignant, which means it may spread throughout the body. It spreads by invading otherwise healthy tissue and it is this process, or metastasis, that makes cancer a life-threatening disease. The second tumor that is formed is called the metastatic tumor.
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Primary sites
Metastatic tumors occur in the latter stages of cancer. The cancer cells break off from the original tumor and travel via the blood and/or lymphatics to a new site. The most common primary sites are the adrenals, liver, brain and bones and some tumors spread to specific parts of the body. For example, prostrate cancer usually spreads to the bones.
Metastatic cells
The cells in a metastatic tumor are like those of the primary tumor so if breast cancer metastasizes to the lung, the disease in the lung is not lung cancer but metastatic breast cancer. In the 10% of cases where the primary site is not evident, it may be possible to find it by examining the tissue of the tumor in evidence. There are also cases where the primary cancer has regressed completely, leaving only the metastatic one.
Angiogenesis
For metastasis to take place, a new network of blood vessels is formed which enable invasion into the cancer and provide it with nutrients and oxygen. The formation of networks of blood vessels, or angiogenesis, is a normal process in growth and development but also a fundamental step in the change of tumors from dormant to malignant.
Treatment
Unfortunately, modern treatment methods are rarely effective in treating metastases. The treatment depends on the original tumor and includes chemotherapy, radiation therapy and surgery.