Metastatic breast cancer is cancer that has spread beyond the primary cancer of the breast to a different site in your body. When breast cancer cells leave the breast, they travel to other sites through the lymph and blood systems and often migrate to the bones, the lungs, the liver and (less commonly) to the brain. There may be other parts of the body where breast cancer cells can spread, such as the skin and adrenal glands. There is no set pattern for where the cancer cells will spread.

If you have had breast cancer before, the metastasis may be referred to as a recurrent disease. This is because some of the cancer cells survived the treatments you previously had and began to grow later.  No one can predict how long cancer cells will be dormant before they begin to grow and can be detected.

You may hear metastatic breast cancer referred to as advanced, secondary or Stage IV breast cancer.

If this is your first diagnosis and you have been told you have metastatic breast cancer, you have cancer in the breast and in other parts of your body.

Even though the cancer cells have spread to other part(s) of your body, you will still be treated for breast cancer. A bone metastases diagnosis is not a bone cancer diagnosis: the cells are still breast cancer cells. Remember that breast cancer treatments should treat the cancer, no matter where it is.

Your doctor may run tests to confirm the cancer cells found in a different area of your body are a metastasis rather than a different type of cancer.

Bone Metastases

Bone metastases can occur in any bone in the body, but are most often found in bones near the centre of the body. The spine is the most common site of bone metastasis. The next common sites are the pelvis (hip), upper leg bone (femur), upper arm bone (humerus), ribs and the skull.

Sometimes when cancer spreads to the bone, calcium can be released into the bloodstream. High blood calcium levels (hypercalcemia) can mimic common symptoms that you may already be experiencing such as constipation, nausea, loss of appetite, fatigue and, in some cases, dehydration (excessive thirst and urine output). Fractures may occur when cancer cells weaken the bone

Bone pain is often the first symptom of cancer that has spread to the bone. The pain often comes and goes at first and the discomfort may range from a dull ache to a more piercing or stabbing pain. However, most bone metastases cause no symptoms at all. Bone metastases are usually detected with bone scans, x-rays or CT (Computed Tomography) scans.

Lung Metastases

Cancer that has spread to your lungs may show up as a tumour that appears as a single mass, or it may spread within the lining of the lung walls. Lung metastases may also cause a build-up of fluids in the lungs or produce scarring that reduces lung capacity and elasticity; these conditions may make breathing difficult. Symptoms such as a cough or shortness of breath may suggest lung metastasis. However, it can be diagnosed without presenting any symptoms. Lung metastases are usually diagnosed from a chest x-ray or a CT scan of the chest.

Liver Metastases

Cancer cells that have spread to your liver tend to spread throughout the liver rather than form a single tumour.  As the cancer grows, the liver tends to expand and the pressure on the outside membrane can become painful. There may be a number of symptoms, including abdominal pain, jaundice, sweating, constipation, decreased appetite, weight loss and, in very serious cases, liver failure. Occasionally, there are no symptoms. Liver metastases are most commonly diagnosed through an abdominal ultrasound or CT scan.

Brain Metastases

Breast cancer cells sometimes travel to your brain. The most common symptom is a headache that is often different from headaches you may have had before. Depending on which areas of the brain are affected, you may have symptoms such as dizziness, general weakness or weakness down one side of the body, unsteadiness, difficulty writing or walking, seizures or double vision. You may also experience nausea, vomiting or fatigue. These symptoms may occur suddenly but they usually develop slowing over time. You may experience some of these symptoms but it is unlikely you will experience all of them.  Remember that many of these symptoms can be attributed to other factors that have nothing to do with brain metastases. Brain metastases can be diagnosed by a CT scan or MRI (Magnetic Resonance Imaging).