Breast Cancer - Metastatic: Diagnosis

Approved by the Cancer.Net Editorial Board, 11/2022

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 to look for metastatic disease may also be performed if a patient is diagnosed with locally advanced breast cancer but doesn't have any symptoms. You can find information on diagnosing breast cancer in the Diagnosis section of the earlier-stage Breast Cancer guide. Testing can also be helpful to learn the status of the disease. Doctors may also do tests to learn which treatments could work best.

How metastatic breast cancer is diagnosed

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

  • Your medical history

  • Your symptoms

  • Your physical examination results

There are different tests used for diagnosing metastatic breast cancer. Your doctor may recommend the following tests to diagnose metastatic breast cancer. Not all tests described here will be used for every person.

  • X-ray. An x-ray creates 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 looks at the inside of the bones using a radioactive tracer. The amount of radiation in the tracer is too low to be harmful. 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 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 scan is a way to create pictures of organs and tissues inside the body. 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 small amount of a radioactive sugar substance is injected into the patient’s veins. 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. However, the amount of radiation in the substance is too low to be harmful. 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 the 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 produces detailed images of the inside of the body using magnetic fields, not x-rays. 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. They also look at 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 can also cause changes in 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 found in a person's blood. They are made by the tumor or by the body in response to the cancer. 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. Some tests may also be done for circulating DNA or circulating tumor cells.

    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 development of metastatic disease, as such testing does not appear to improve a patient’s chance of recovery. Treatment options and changes to treatment are primarily based on factors other than biomarkers, such as how much and where the tumor has grown and your overall health and treatment preferences.

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 only way to make a definite diagnosis, even if other tests can suggest that cancer is present. During a biopsy, a small amount of tissue is removed for examination under a microscope. A biopsy can be done from 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 lessen discomfort. A pathologist will 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 the genes in a cancer cell. 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.

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

    • PD-L1. This protein can be found on the surface of cancer cells and some of the body's immune cells. It 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. This is a specific genetic change found in many cancers, including some breast cancers.

    • PIK3CA. This genetic mutation is common in metastatic breast cancer.

  • 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 or if you have a specific type of breast cancer, such as triple negative. Results from genetic testing may be used for identifying treatment options, especially for people who have mutations in BRCA1 or BRCA2. In addition, 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 who could also have the genetic change. Learn more about inherited breast cancer risk.

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

For many 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 and

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.