Cancer can form in any tissue of the body and can spread from the primary
site (the place where the cancer first began to grow) to other parts of
the body. Cancer that has spread from the place in which it started to
other parts of the body is called metastatic cancer. Metastatic cancer
cells usually look like cells in the type of tissue where the cancer
began. For example, breast cancer cells that spread to the lung look like
breast cancer cells, not lung cancer cells. Sometimes metastatic cancer
cells are found in the body, but tests do not find a primary tumor. If
cancer cells are found in the body but the place where the cancer started
cannot be identified, the disease is called cancer of unknown primary
site. Treatment is based on what the cancer cells look like under a
microscope, the patient's symptoms, and the extent of the cancer in the
body. Treatment is usually chemotherapy or radiation therapy. |
