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Metastatic Breast Cancer: Metas...

Metastatic Breast Cancer: Metastasis and Primary Cancer

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Metastatic Breast Cancer is breast cancer that spreads to other organs or to lymph nodes far from the primary tumor in the tissue of the breast, and is also known as Stage IV Breast Cancer.


What is metastasis, and how does it happen?

Metastasis means the spread of cancer. Cancer cells can break away from a primary tumor and enter the bloodstream or lymphatic system (the system that produces, stores, and carries the cells that fight infections). That is how cancer cells spread to other parts of the body. Doctors sometimes refer to metastatic cancer as distant disease or stage four cancer.

When cancer cells spread and form a new tumor in a different organ, the new tumor is a metastatic tumor. The cells in the metastatic tumor come from the original tumor. This means, for example, that if breast cancer spreads to the lungs, the metastatic tumor in the lung is made up of cancerous breast cells (not lung cells). In this case, the disease in the lungs is metastatic breast cancer (not lung cancer). Under a microscope, metastatic breast cancer cells generally look the same as the cancer cells in the breast.


How does a doctor know whether a cancer is a primary or a metastatic tumor?

To determine whether a tumor is primary or metastatic, a pathologist examines a sample of the tumor under a microscope. In general, cancer cells look like abnormal versions of cells in the tissue where the cancer began. Using specialized diagnostic tests, a pathologist is often able to tell where the cancer cells came from. Markers or antigens found in or on the cancer cells can indicate the primary site of the cancer.

Metastatic cancers may be found before or at the same time as the primary tumor, or months or years later. When a new tumor is found in a patient who has been treated for cancer in the past, it is more often a metastasis than another primary tumor.


Is it possible to have a metastatic tumor without having a primary cancer?

No. A metastatic tumor always starts from cancer cells in another part of the body. In most cases, when a metastatic tumor is found first, the primary tumor can be found. The search for the primary tumor may involve lab tests, x-rays, and other procedures. However, in a small number of cases, a metastatic tumor is diagnosed but the primary tumor cannot be found, in spite of extensive tests. The pathologist knows the tumor is metastatic because the cells are not like those in the organ or tissue in which the tumor is found. Doctors refer to the primary tumor as unknown or occult (hidden), and the patient is said to have cancer of unknown primary origin (CUP). Because diagnostic techniques are constantly improving, the number of cases of CUP is going down.


Source: Compiled from information from the National Cancer Institute (NCI), a division of the National Institutes of Health (NIH).

NCI health-related material is provided for information purposes only and does not necessarily represent endorsement by or an official position of the National Cancer Institute or any other Federal Agency. Advice on the treatment or care of an individual patient should be obtained through consultation with a physician who has examined that patient or is familiar with that patient's medical history.

  • See also:

                  o  Metastatic Breast Cancer- Overview

                  o  Metastatic Breast Cancer- Risk factors, detection, prognosis, prevention






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Start Date
Sep 16, 2010
by MedHelp Editor
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Sep 16, 2010
by MedHelp Editor