The most common sites for breast cancer to spread (and methods for localized treatment) are:
I have metastatic lobular cancer…how is that different?
- Lymph nodes Under the arm (or axilla, called axillary nodes) or along the center of the rib cage (internal mammary nodes) or near the collar bone (supraclavicular nodes).
Muscle, fatty tissue and skin – usually in the area near where the initial tumor was, for example the muscles of the chest wall or on the surgical scar. Breast cancer that spreads only to these areas may have a somewhat better prognosis—if it has spread through direct extension through tissue surrounding the original cancer, or through the lymphatic system, and not through the circulatory system. While sometimes removed surgically or subjected to radiation treatment, these metastatic sites often (but not invariably) will turn out to be early indicators of widespread metastatic disease. The main treatment is usually systemic, therefore, in an attempt to delay the spread of the cancer to distant metastatic sites.
- Bones – breast cancer can spread to many parts of the skeleton, but the ribs, spine, pelvis and long bones of the arms and legs are the most common metastatic sites. Persistent pain, achiness, or tenderness on pressure are usually the first symptom of bone metastases. Bone metastases are of two kinds, or may have mixed features. Osteolytic bone metastases, where the bone is eaten away, have a characteristic “Swiss cheese” appearance on scans, and may cause weakening and even fracture of weight-bearing bones, although this is less common now that IV bisphosphonates are routinely given. Osteoblastic bone metastases can cause growth of unhealthy bone that leads to pain. Less commonly, numbness or problems with bowel or bladder control can be a sign that bone metastases are causing spinal cord compression. This should be considered a medical emergency, since this can lead to permanent loss of function. Immediate focalized radiation or surgery is usually required.
- Bone marrow - cancer cells in the bone marrow are often present with metastatic breast cancer, especially when there are bone metastases, but may go undetected until there is a significant and growing decrease in white or red cell counts that is unrelated to lowered counts from chemotherapy. A finding like this may lead an oncology to order a bone marrow biopsy, which can confirm the diagnosis. For these patients, a delicate balance that must be struck with effective chemotherapy drugs to control bone marrow metastases that at the same time depress the bone marrow.
- Liver – because the blood supply is filtered by the liver, this is a very common site for breast cancer to spread. Often, there are no symptoms of liver metastases until enough of the liver is affected to alter liver enzymes. For this reason, blood levels of these enzymes are usually monitored during treatment. Because women with metastatic breast cancer are on continuous treatment, adequate liver function is crucial to detoxify the often harsh drugs that are given. While systemic treatment usually serves to control liver metastases, because the liver is a vital organ, some localized treatments of the liver are now being tested for women who have no or minimal disease elsewhere in their bodies. It is unclear whether methods including surgical removal, radioembolization, radiofrequency ablation, and chemoembolization actually extend women’s lives.
- Lungs – since the body’s bloodstream also passes through the lungs, this too is a common metastatic site. When there are many small nodules on the outside of the lung, this can cause pleural effusion, where the pleural sac surrounding the lung fills with fluid, which can compress the lung. Shortness of breath can result from pleural effusion, or from growth of a metastatic tumor blocking air flow. Removing the fluid from the pleural space, known as thoracentesis, can bring dramatic relief of shortness of breath, but the fluid often reaccumulates, making pleuradesis necessary, where the pleural sac is sealed to the outside of the lungs with talc or an antibiotic. Sometimes a pleural tap can be used.
Brain - Although any kind of metastatic breast cancer can spread to the brain, certain kinds are more likely to do so. These kinds are HER2-positive and so-called �triple negative� (basal like) that doesn't overexpress the proteins made by either the HER2 gene or the estrogen or progesterone receptor genes. A third or more of patients with HER2-positive metastatic breast cancer will develop brain metastases. Most of these will be diagnosed from symptoms related to pressure exerted by the growing tumor: headache, seizure, visual disturbances, dizziness. Brain metastases are treated primarily with radiation and steroids to reduce the swelling. Depending upon the number and size of brain metastases, the whole brain may be irradiated or it may be possible to use stereotactic radiosurgery to treat just the metastasis. Large tumors may be treated with surgery (craniotomy) to remove the tumor, if in an operable part of the brain. For more information on brain and other central nervous system metastases see BrainMetsBC.org.
- Other parts of the body - While these are the most common sites for metastatic breast cancer to spread, other sites are not unusual.
Lobular cancer, when it metastasizes, may have a different pattern of spread, tending to spread to the abdomen and the lining of the gastrointestinal system, much like ovarian cancer. Metastatic sites include the ovary, peritoneum, stomach and omentum. Sometimes the function of the ureters and bile ducts can be affected. Lobular metastases often grow in sheets of cells, rather than in lumps, and thus may be hard to follow on scans.