Breast Cancer - Metastatic: Diagnosis

Approved by the Lineagotica Editorial Board, 04/2019

ON THIS PAGE: You will find a list of common tests, procedures, and scans that doctors use to find out the cause of a medical problem. Use the menu to see other pages.

If metastatic breast cancer develops, it may or may not cause symptoms. Sometimes these symptoms may lead a doctor to perform tests to find metastatic breast cancer or learn if an earlier breast cancer has metastasized. Testing for metastatic disease may also be performed if a patient is diagnosed with locally advanced breast cancer. You can find information on breast cancer staging in the Diagnosis section of the earlier-stage Breast Cancer guide. Testing can also be helpful to follow the status of the disease. Doctors may also do tests to learn which treatments could work best.

Your doctor may consider these factors when choosing a diagnostic test:

  • Your medical history

  • Your symptoms

  • The location of the breast cancer in your body

  • Your physical examination results

Your doctor may recommend the following tests to diagnose metastatic breast cancer. Not all tests listed below will be used for every person.

  • X-ray. An x-ray is a way to create a picture of the structures inside of the body, using a small amount of radiation. A chest x-ray may be used to look for cancer that has spread from the breast to the lungs.

  • Bone scan. A bone scan may be used to look for spread of cancer to the bones. The scan uses a radioactive tracer to look at the inside of the bones. The tracer is injected into a patient’s vein. It collects in areas of the bone and is detected by a special camera. Healthy bone appears lighter to the camera, and areas of injury, such as those caused by the cancer, stand out on the image. Some cancers do not cause the same healing response and will not show up on the bone scan. Areas of advanced arthritis or healing after a fracture will also appear dark.

  • Computed tomography (CT or CAT) scan. A CT scan may be used to look for tumors in organs outside of the breast, such as the lung, liver, bone, and lymph nodes. A CT scan takes pictures of the inside of the body using x-rays taken from different angles. A computer combines these pictures into a detailed, 3-dimensional image that shows any abnormalities or tumors. A CT scan can be used to measure the tumor’s size. Sometimes, a special dye called a contrast medium is given before the scan to provide better detail in the image. The dye can be injected into a patient’s vein and/or given as a liquid to swallow.

  • Positron emission tomography (PET) or PET-CT scan. A PET-CT scan may also be used to find out whether the cancer has spread to organs outside of the breast. A PET scan is usually combined with a CT scan (see above), called a PET-CT scan. However, you may hear your doctor refer to this procedure just as a PET scan. A PET scan is a way to create pictures of organs and tissues inside the body. A small amount of a radioactive sugar substance is injected into the patient’s body. This sugar substance is taken up by cells that use the most energy. Because cancer tends to use energy actively, it absorbs more of the radioactive substance. A scanner then detects this substance to produce images of the inside of the body.

    Areas that are most active appear as bright spots, and the intensity of the brightness can be measured to better describe these areas. A PET-CT scan may also be used to measure the size of tumors and to determine the location of the bright spots more accurately. A PET-CT scan will also show any abnormalities in the bone, similar to a bone scan (see above).

  • Magnetic resonance imaging (MRI). An MRI uses magnetic fields, not x-rays, to produce detailed images of the body. MRI can be used to measure the tumor’s size. A special dye called a contrast medium is given before the scan to create a clearer picture. This dye is usually injected into a patient’s vein.

  • Serum chemistry blood tests. These tests are often done to look at minerals in your blood, such as potassium and calcium, and specialized proteins called enzymes that can be abnormal if cancer has spread. These tests can also evaluate how well the liver and kidneys are working. Although these test results can be abnormal if cancer has spread in the body, many noncancerous conditions also cause changes in the test results.

  • Complete blood count (CBC). A complete blood count (CBC) measures the number of different types of cells, such as red blood cells and white blood cells, by testing a sample of a person’s blood. It is done to make sure that your bone marrow is working well.

  • Blood tumor marker tests. Serum tumor markers or biomarkers are tumor proteins in a person's blood. Higher levels of a serum tumor marker may be due to cancer or a noncancerous condition. For metastatic breast cancer, testing may be done for cancer antigen 15-3 (CA 15-3), cancer antigen 27.29 (CA 27.29), and/or carcinoembryonic antigen (CEA). These biomarkers may be found in the blood of people with breast cancer. However, abnormal levels of these biomarkers may also be a sign of another condition that is not cancer.

    Tumor marker testing may be useful to monitor the growth of recurrent or metastatic disease along with symptoms and imaging tests. The actual level of a tumor marker at any single time is less important than the changes in the levels over time. Decreasing levels of tumor markers usually mean that the treatment is working to shrink the cancer.

    Tumor markers should not be used to monitor for a recurrence, as such testing does not appear to improve a patient’s chance of recovery.

Analyzing the cancer

One of the most important tests when someone is diagnosed with metastatic breast cancer is a tumor biopsy. A biopsy is the removal of a small amount of tissue for examination under a microscope. A biopsy can be done for many parts of the body, including lymph nodes, lungs, liver, bone, skin, or body fluids. The procedure is usually performed with guidance from a CT scan or ultrasound. Pain medication is used during this procedure to prevent discomfort. A pathologist will then analyze the tissue sample. A pathologist is a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease.

If you are diagnosed with metastatic breast cancer, your doctor may perform a biopsy to evaluate the features of the cancer and find out if they have changed in any way if you had an earlier diagnosis of breast cancer. These results are very important. Testing helps to determine the subtype of breast cancer, which is used to choose treatment options.

Standard testing of metastatic breast cancer looks at 3 important receptors:

Additional testing may also be done. For example, testing the tumor DNA may find mutations in the cancer’s genes. This can help the doctor determine how the cancer will behave and can help identify potential treatment options. The following testing may be done to look at cancer genes:

  • Genomic testing. Genomics is the study of how the genes in a cancer cell behave. Genomic tests look at the genes in breast cancer to help determine what is causing the cancer to grow. The information from these tests can help the cancer care team understand how the cancer may behave and help guide treatment decisions.

  • Molecular testing of the tumor. Your doctor may recommend running other laboratory tests on a tumor sample to identify specific genes, proteins, and other factors unique to the tumor. If you have locally advanced or metastatic breast cancer, your doctor may recommend testing for the following molecular features:

    • PD-L1, which is found on the surface of cancer cells and some of the body's immune cells. This protein stops the body’s immune cells from destroying the cancer.

    • Microsatellite instability-high (MSI-H) or DNA mismatch repair deficiency (dMMR). Tumors that are MSI-H or have a dMMR have difficulty repairing damage to their DNA. This means that they develop many mutations or changes. These changes produce abnormal proteins on the tumor cells that make it easier for immune cells to find and attack the tumor.

    • NTRK gene fusions, which is a specific genetic change found in a range of cancers, including breast cancer. 

    • PIK3CA gene mutations, which have been found in around 40% of advanced ER-positive breast cancers.

  • Genetic testing. Genetic testing looks at the genes inherited from a person’s parents. Genetic testing may be recommended if you have a family history of breast cancer. Finding out whether you have a genetic change linked with an increased risk of breast cancer may be important to other members of your family that could also have the genetic change. Learn more about inherited breast cancer risk.

After diagnostic tests are done, your doctor will review all of the results with you. You will find out more about the cancer, its location, and the tumor subtype.

For most patients, a diagnosis of metastatic breast cancer comes as a shock. People describe a range of emotions such as fear, anger, or sadness that may change day-to-day or over time. You may have concerns about how this diagnosis will affect many different aspects of your life, such as your relationships, work or career, family and social roles, and finances. You may be worried about suffering or having your life shortened by this disease. It is important to remember you are not alone.

Patients and their families are encouraged to talk about the way they are feeling with doctors, nurses, social workers, or other members of the health care team. It may also be helpful to talk with other people with metastatic breast cancer, such as through a support group.

Information about the cancer will help the doctor recommend a specific treatment plan. The next section in this guide is Types of Treatment. Use the menu to choose a different section to read in this guide.