Metastasis means the spread of cancer. Metastatic breast cancer occurs when breast cancer cells break away from the original tumor and spread past the breast and axillary (underarm) lymph nodes in the bloodstream or lymphatic system (the system that produces, stores, and carries the cells that fight infections) to other sites (such as bone or liver) of the body. Metastatic breast cancer is also classified as stage IV or advanced breast cancer.
When breast cancer cells spread and form a new tumor in a distant organ, the new tumor is a metastatic breast tumor. The cells in the metastatic tumor come from the original tumor. This means 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.
Although breast cancer cells can potentially spread to almost any part of the body, the most common area breast cancer spreads is to bone, followed by the lungs and liver.
Some people with metastatic cancer do not have symptoms. Their metastases are found by x-rays and other tests performed for other reasons.
When symptoms of metastatic breast cancer occur, the type and frequency of the symptoms will depend on the size and location of the metastasis. For example, cancer that spreads to the bones is likely to cause pain and can lead to bone fractures.
Treatment of metastatic breast cancer often focuses on relieving symptoms and extending a woman's lifetime.
When cancer has metastasized, it may be treated with chemotherapy, radiation therapy, hormone therapy, biological targeted therapy, surgery or a combination of these. The choice of treatment depends on the size and location of the metastasis, the patient's age and general health, and the types of treatments the patient has had in the past. For patients diagnosed with Stage IV breast cancer that is hormone receptor positive, hormonal therapy may be the first line of defense against the disease.
Yes, new treatments are under study. Research studies of new treatments often begin with treatment of metastatic breast cancer. The results of such studies have also led to progress not only in the treatment of cancer, but in the detection, diagnosis, and prevention of the disease as well.
Although there is no cure for metastatic breast cancer, many treatments can extend a patient's life and maintain quality of life.
The content on this page was reproduced, in whole or in part, from the National Cancer Institute (NCI) website at www.cancer.gov.