Breast Cancer: Diagnosis

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

Doctors use many tests to find, or diagnose, breast cancer. They also do tests to learn if the cancer has spread to a part of the body other than the breast and the lymph nodes under the arm. If this happens, it is called a metastasis (See the Metastatic Breast Cancer guide for more information). Doctors may also do tests to learn which treatments could work best.

For most types of cancer, a biopsy is the only sure way for the doctor to know if an area of the body has cancer. In a biopsy, the doctor takes a small sample of tissue for testing in a laboratory.

This section describes options for diagnosing this type of cancer. Not all tests listed below will be used for every person. Your doctor may consider these factors when choosing a diagnostic test:

  • The type of cancer suspected

  • Your signs and symptoms

  • Your age and general health

  • The results of earlier medical tests

The series of tests needed to evaluate a possible breast cancer usually begins when a woman or her doctor discover a mass or abnormal calcifications on a screening mammogram, or a lump or nodule in the woman’s breast during a clinical or self-examination. Less commonly, a woman might notice a red or swollen breast or a mass or nodule under the arm.

The following tests may be used to diagnose breast cancer or for follow-up testing after a breast cancer diagnosis.

Imaging tests

Imaging tests show pictures of the inside of the body. The following imaging tests of the breast may be done to learn more about a suspicious area found in the breast during screening. In addition to these, there are other newer types of tests that are being studied.

  • Diagnostic mammography. Diagnostic mammography is similar to screening mammography except that more pictures of the breast are taken. It is often used when a woman is experiencing signs, such as a new lump or nipple discharge. Diagnostic mammography may also be used if something suspicious is found on a screening mammogram.

  • Ultrasound. An ultrasound uses sound waves to create a picture of the breast tissue. An ultrasound can distinguish between a solid mass, which may be cancer, and a fluid-filled cyst, which is usually not cancer.

  • MRI. An MRI uses magnetic fields, not x-rays, to produce detailed images of the body. A special dye called a contrast medium is given before the scan to help create a clear picture of the possible cancer. This dye is injected into a patient’s vein. A breast MRI may be used after a woman has been diagnosed with cancer to check the other breast for cancer or to find out how much the disease has grown throughout the breast. Breast MRI is also a screening option, along with mammography, for some women with a very high risk of developing breast cancer (see Risk Factors and Prevention).


A biopsy is the removal of a small amount of tissue for examination under a microscope. Other tests can suggest that cancer is present, but only a biopsy can make a definite diagnosis. A pathologist then analyzes the sample(s). A pathologist is a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease. There are different types of biopsies, classified by the technique and/or size of needle used to collect the tissue sample.

  • Fine needle aspiration biopsy. This type of biopsy uses a thin needle to remove a small sample of cells.

  • Core needle biopsy. This type uses a wider needle to remove a larger sample of tissue. This is usually the preferred biopsy technique for finding out whether an abnormality on a physical examination or an imaging test is cancer. Local anesthesia, which is medication to block pain, is used to lessen a patient’s discomfort during the procedure.

  • Surgical biopsy. This type removes the largest amount of tissue. Because surgery is best done after a cancer diagnosis has been made, a surgical biopsy is usually not the recommended way to diagnose breast cancer. Most often, non-surgical core needle biopsies are recommended to diagnose breast cancer.

  • Image-guided biopsy. During this procedure, a needle is guided to the location with the help of an imaging technique, such as mammography, ultrasound, or MRI. A stereotactic biopsy is done using mammography to help guide the needle. A small metal clip is usually put into the breast to mark where the biopsy sample was taken, in case the tissue is cancerous and more surgery is needed. This clip is usually titanium so it will not cause problems with future imaging tests, but check with your doctor before you have any imaging tests. An image-guided biopsy can be done using a fine needle, core, or vacuum-assisted biopsy (see above), depending on the amount of tissue being removed. Imaging tests may also be used to find the best place to take a biopsy sample of a lump that can be felt.

  • Sentinel lymph node biopsy. This procedure is a way to find out if there is cancer in the lymph nodes near the breast. Learn more about sentinel lymph node biopsy in the Types of Treatment section.

Analyzing the biopsy sample

Analyzing the sample(s) removed during the biopsy can help your doctor learn about specific features of a cancer that help determine treatment options.

  • Tumor features. Examination of the tumor under the microscope is used to determine if it is invasive or in situ, ductal or lobular, and whether the cancer has spread to the lymph nodes. The margins or edges of the tumor are also examined and their distance from the tumor is measured, which is called margin width.

  • ER and PR. Testing for ER and PR (see Introduction) helps determine both the patient’s risk of recurrence and the type of treatment that is most likely to lower the risk of recurrence. ER and PR are often measured for DCIS as well. Generally, hormonal therapy (see Types of Treatment) works well for ER-positive and/or PR-positive cancers. Learn about ER and PR testing recommendations from ASCO and the College of American Pathologists (CAP).

  • HER2. The HER2 status (see Introduction) helps determine whether drugs that target the HER2 receptor, such as trastuzumab (Herceptin, Herzuma, Ogivri, Ontruzant), might help treat the cancer. This test is only done on invasive cancers. ASCO and CAP recommend that HER2 testing is done when you are first diagnosed with an invasive breast cancer. If the cancer has spread to another part of your body or comes back after treatment, testing should be done again on the new tumor or areas where the cancer has spread, especially if results would influence your treatment options.

    HER2 tests are usually clearly positive or negative, meaning that your cancer has either a high or low level of HER2. If your test results are not clearly positive or negative, testing may need to be done again, either on a different tumor sample or with a different test. Sometimes, even with repeated testing, the results may not be conclusive so you and your doctor will have to discuss the best treatment option.

    If the cancer is HER2 positive, HER2-targeted therapy may be a recommended treatment option for you. If the cancer is HER2 negative, HER2-targeted therapy is not a treatment option for you, and your doctor will give you other options for treating the breast cancer. Learn more about recommendations from ASCO and CAP, found on ASCO’s website.


  • Grade. The tumor grade is also determined from a biopsy. Grade refers to how different the cancer cells look from healthy cells, and whether they appear slower growing or faster growing. If the cancer looks similar to healthy tissue and has different cell groupings, it is called "well differentiated" or a "low-grade tumor." If the cancerous tissue looks very different from healthy tissue, it is called "poorly differentiated" or a "high-grade tumor." There are 3 grades: grade 1 (well differentiated), grade 2 (moderately differentiated), and grade 3 (poorly differentiated).

  • 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 have MSI-H or dMMR have difficulty repairing damage to their DNA. This means that they develop many mutations or changes. These changes make 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.

    • PI3KCA gene mutation, which is a specific genetic change commonly found in breast cancer.

Results of these tests can help determine your treatment options.

Genomic tests to predict recurrence risk

Doctors use genomic tests to look for specific genes or substances made by the genes called proteins that are found in or on cancer cells. These tests help doctors better understand the unique features of each patient’s breast cancer. Genomic tests can also help estimate the risk of the cancer coming back after treatment. Knowing this information helps doctors and patients make decisions about specific treatments and can help some patients avoid unwanted side effects from a treatment that may not be needed.

The genomic tests listed below can be done on a sample of the tumor that was already removed during biopsy or surgery. Most patients will not need an extra biopsy or more surgery for these tests.

  • Oncotype Dx™. This test is an option for people with ER-positive and/or PR-positive, HER2-negative breast cancer that has not spread to the lymph nodes. This test can help patients and their doctors make decisions about whether chemotherapy should be added to hormonal therapy. This test looks at 16 cancer-related genes and 5 reference genes to calculate a “recurrence score” that estimates the risk of the cancer coming back within 10 years after diagnosis. The recurrence score is used to guide recommendations on the use of chemotherapy, which may also differ by age. The recommendations are listed by age group below.

For patients age 50 or younger

    • Recurrence score less than 16: Chemotherapy is generally not needed along with hormonal therapy

    • Recurrence score of 16 to 30: Chemotherapy may be added to hormonal therapy

    • Recurrence score of 31 or higher: Chemotherapy is usually added to hormonal therapy

For patients older than 50

    • Recurrence score less than 26: Chemotherapy is generally not needed along with hormonal therapy

    • Recurrence score of 26 to 30: Chemotherapy may be added to hormonal therapy

    • Recurrence score of 31 or higher: Chemotherapy is usually added to hormonal therapy

  • MammaPrint™. This test is an option for people with ER-positive and/or PR-positive, HER2-negative breast cancer that has not spread to the lymph nodes or has only spread to 1 to 3 lymph nodes. This test uses information from 70 genes to estimate the risk of recurrence for early-stage breast cancer. For people with a high risk of the cancer coming back, this test can help patients and their doctors make decisions about whether chemotherapy should be added to hormonal therapy. This test is not recommended for people with a low risk of the cancer coming back.

  • Breast Cancer Index™. This test is an option for people with ER-positive and/or PR-positive, HER2-negative breast cancer that has not spread to the lymph nodes. This test may help patients and their doctors make decisions about how long a patient should receive hormonal therapy.

  • Additional tests. There are additional tests that may be options for people with ER-positive and/or PR-positive, HER2-negative breast cancer that has not spread to the lymph nodes. These tests include PAM50 (Prosigna™), EndoPredict, and uPA/PAI and can also be used to estimate how likely a cancer will spread to other parts of the body.

The tests listed above have not been shown to be useful to predict risk of recurrence for people with HER2-positive or triple-negative breast cancer. Therefore, none of these tests are currently recommended for breast cancer that is HER2 positive or triple negative. Your doctor will use other factors to help recommend treatment options for you.

Talk with your doctor for more information about genomic tests, what they mean, and how the results might affect your treatment plan.

This information is based on ASCO recommendations for the Use of Biomarkers to Guide Decisions on Adjuvant Systemic Therapy for Women with Early-Stage Invasive Breast Cancer and ASCO’s endorsement of recommendations from Cancer Care Ontario on the Role of Patient and Disease Factors in Adjuvant Systemic Therapy Decision-Making for Early-Stage, Operable Breast Cancer. Please note that these links take you to another ASCO website.

Blood tests

The doctor may also need to do several types of blood tests. These tests may be done before or after surgery.

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

  • Blood chemistry. This test evaluates how well your liver and kidneys are working.

  • Hepatitis tests. These tests are occasionally used to check for evidence of prior exposure to hepatitis B and/or hepatitis C. If you have evidence of an active hepatitis B infection, you may need to take a special medication to suppress the virus before you receive chemotherapy. Without this medication, the chemotherapy can cause the virus to grow and damage the liver. Learn more about hepatitis B screening before treatment.

After diagnostic tests are completed, your doctor will review all of the results with you. If the diagnosis is cancer, these results also help the doctor describe the cancer. This is called staging. Depending on the stage of the cancer, additional imaging tests may be recommended. If there is a suspicious area found outside of the breast and nearby lymph nodes, you may need a biopsy of other parts of the body to find out if it is cancer.

The next section in this guide is Stages. It explains the system doctors use to describe the extent of the disease. Use the menu to choose a different section to read in this guide.