Breast cancer metastasis is the spread of cancer cells to a new part of the body, away from the original site of cancer. An explanation of metastasis should first point out the difference between the local spread of cancer and this metastatic cancer. Local spread of breast cancer means the original tumor has grown into the nearby tissues. An example of this is a breast tumor which has also attached itself to the chest wall next to the breast. Breast cancer metastasis (also called metastatic breast cancer) means the cancer cells entered either the blood stream or the lymph system, spread to another area of the body (either lymph nodes or more distant parts, like other organs) and started to grow their abnormal cells in that location.

To further clarify, the lymph system is comprised of very small vessels, similar to veins that carry both waste products from cells and also cells used in the body’s immune system. When cancer cells from a breast tumor break off, they can enter this lymph system and travel to lymph nodes where they start to grow, forming a breast cancer metastasis.

Cells from a breast tumor can also enter the bloodstream and travel to other areas of the body and locate, again what is called a breast cancer metastasis. It should be noted that different cancers have affinities for different parts of the body; breast cancer has a tendency to locate in bones, liver and lungs.

The breast cancer metastasis can occur early, with the original discovery of the cancerous tumor, or it can develop later on after the woman’s treatment is complete, often within two to five years. At the time of the discovery of the first tumor, the testing a woman undergoes is necessary to detect if a metastasis has occurred or not, because this has great influence on her program for treatment.

Whether due to better screening and earlier discovery of tumors, or due to new treatment methods, survival with breast cancer metastasis is improving. There are newer chemotherapy drugs, drugs for women with HER2-positive cancers, and aromatase inhibitors for hormone-receptor-positive tumors. There is much research being conducted, especially in these areas of recurrence and breast cancer metastasis.