Journal of Clinical & Experimental Pathology
Open Access

Metastatic breast cancer, also referred to as metastases, advanced breast cancer, secondary tumours, secondaries, or stage IV breast cancer, is a stage of breast cancer where the breast cancer cells have spread to distant sites beyond the axillary lymph nodes [1]. There is no cure for metastatic breast cancer it often can be effectively treated. There is no stage after IV.

Metastases can occur several years after the primary breast cancer, although it is sometimes diagnosed at the same time as the primary breast cancer or, rarely, before the primary breast cancer has been diagnosed.

Metastatic breast cancer cells frequently differ from the preceding primary breast cancer in properties such as receptor status [2]. The cells have often developed resistance to several lines of previous treatment and have acquired special properties that permit them to metastasize to distant sites. Metastatic breast cancer can be treated, sometimes for many years, but it cannot be cured. Distant metastases are the cause of about 90% of deaths due to breast cancer.

Breast cancer can metastasize anywhere in body but primarily metastasizes to the bone, lungs, regional lymph nodes, liver, and brain, with the most common site being the bone [3,4]. Treatment of metastatic breast cancer depends on location of the metastatic tumors and includes surgery, radiation, chemotherapy, biological, and hormonal therapy.

Cancer begins when healthy cells change and grow out of control, forming a mass or sheet of cells called a tumor. A tumor can be cancerous or benign. A cancerous tumor is malignant, meaning it can grow and spread to other parts of the body [5]. A benign tumor means the tumor can grow but will not spread.

When breast cancer is limited to the breast and/or nearby lymph node regions, it is called early stage or locally advanced. Read about these stages in a different guide on Cancer.Net [6]. When breast cancer spreads to an area farther from where it started, doctors say that the cancer has “metastasized.” They call the area of spread a “metastasis,” or “metastases” if the cancer has spread to more than 1 area. The disease is called metastatic breast cancer [7]. Another name for metastatic breast cancer is “Stage IV Breast Cancer.”

Doctors may also call metastatic breast cancer Advanced Breast Cancer.” However, this term should not be confused with “Locally Advanced Breast Cancer,” which is breast cancer that has spread to nearby tissues or lymph nodes but not to other parts of the body.

Metastatic breast cancer may spread to any part of the body. It most often spreads to the bones, liver, lungs and brain. Even after cancer spreads, it is still named for the area where it began [8]. This is called the “primary site” or “primary tumor.” For example, if breast cancer spreads to the lungs, doctors call it metastatic breast cancer, not lung cancer. This is because the cancer started in breast cells.

Metastatic breast cancer can develop when breast cancer cells break away from the primary tumor and enter the bloodstream or lymphatic system. These systems carry fluids around the body [9]. The cancer cells are able to travel in the fluids far from the original tumor. The cells can then settle and grow in a different part of the body and form new tumors.

Most commonly, doctors diagnose metastatic breast cancer after a person previously received treatment for an earlier stage (non- metastatic) breast cancer. Doctors sometimes call this a “distant recurrence” or “metastatic recurrence.”

Sometimes, a person’s first diagnosis of breast cancer is when it has already spread. Doctors call this “de novo” metastatic breast cancer.