Is Metastatic Breast Cancer Malignant?

What Is Malignancy?

Tumors, or abnormal clusters of cells, are classified as either benign or malignant. Benign tumors pose few or no health risk and do not grow or spread to other organs. Malignant tumors, however, are capable of invading neighboring tissue or spreading to organs in other parts of the body. All malignant tumors are cancerous and all have the ability to metastasize. However, a tumor can be malignant but may not have metastasized at the time it is detected.

Metastasis is an essential characteristic of a cancer cell. In normal healthy cells, chemical signals trigger growth, division and death. Cancer cells lack these mechanisms and grow too large, replicate too quickly and they fail to die off, accumulating to form tumors. Cancer cells also lack a mechanism that halts growth when a neighboring cell is encountered. The cancer cell continues to grow and invade healthy cells and tissues, altering its environment chemically to allow continued growth while creating its own network of blood vessels for fuel.

Theoretically, every woman who has had breast cancer, even if treated successfully, has a risk of the cancer recurring in the same breast area or in another organ. Breast cancer metastasizes when cancerous cells break off from the tumor and enter the bloodstream or lymph nodes and are carried throughout the body. If it metastasizes, breast cancer most frequently spreads to the underarm lymph nodes, bone, lung, liver or brain. Metastasized tumors often have no symptoms and are detected through routine X-rays or other tests. The cells of the secondary, metastasized tumor are similar to the cells of the original, or primary, tumor. Thus, breast cancer that has metastasized to the lung is considered breast cancer and is treated as such. A pathologist examines the cells of the secondary tumor to determine the primary source. Cancers that start in other organs rarely metastasize to the breast.

Breast cancer may metastasize even if the breast and lymph nodes are removed in a radical mastectomy. The cancerous cells may break off the tumor during surgery, or they may have migrated before the tumor was detected. The risk of metastasis is higher if the lymph nodes are involved when the primary breast tumor is detected and if the tumor is large. After the primary tumor is treated either with surgery (mastectomy or lumpectomy) or radiation therapy, a course of adjuvant chemotherapy is often administered to eradicate any remaining cancer cells.

Metastatic breast cancer treatment depends on several factors, including the type of the primary tumor (that is, whether the primary breast tumor was hormone-receptor-positive or --negative), the size and location of the metastasized tumor, the previous treatment used on the primary tumor and the woman's age and overall health. Typical treatments for metastatic breast cancer include chemotherapy, radiation therapy, surgery, hormonal therapy or targeted therapy.