Breast Cancer: Diagnosis

Approved by the Lineagotica Editorial Board, 10/2018

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 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 list 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 has been diagnosed.

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.

  • Diagnostic mammographyDiagnostic 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 can be injected into a patient’s vein or given as a pill or liquid to swallow. 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).


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. This means that only 1 surgical procedure is needed to remove the tumor and to take samples of the lymph nodes.

  • 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 may be 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 help do a biopsy on a lump that can be felt, to help find the best location.

  • 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, for example the antibody treatment trastuzumab (Herceptin, Ogivri), might help treat the cancer. This test is only done on invasive cancers. ASCO and the College of American Pathologists (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 contains 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.

Results of these tests can help determine your treatment options.

Genomic tests to predict recurrence risk

Tests that take an even closer look at the biology of the tumor may be used to understand more about the breast cancer. These tests can help estimate the risk of cancer recurrence in the years after diagnosis. They can also predict whether a treatment can reduce the risk of cancer recurrence. This helps some patients avoid the possible side effects of a treatment that is not likely to work well.

The tests described below are typically done on tissue removed during surgery. Most patients will not need an extra biopsy or more surgery. For more information about genomic tests, what they mean, and how the results might affect your treatment plan, talk with your doctor.

  • Oncotype Dx™. This test evaluates 16 cancer-related genes and 5 reference genes to estimate the risk of the cancer coming back within 10 years after diagnosis. The test is typically used for women with stage I or stage II (see Stages) ER-positive, HER2-negative breast cancer who will receive hormonal therapy. Results are mainly used to help make decisions about whether chemotherapy should be added to a person’s treatment with hormonal therapy. This test is typically used for people with breast cancer that has not spread to the lymph nodes. But recent research suggests that this test may be useful for some people with breast cancer that has spread to the lymph nodes.

  • Breast Cancer Index™: This test may help make decisions about how long a woman should receive endocrine therapy.

  • MammaPrint™. This test uses information from 70 genes to predict the risk of the cancer coming back for early-stage, low-risk breast cancer. It estimates the risk of recurrence in early-stage breast cancer. In addition, it can help determine if chemotherapy could an option along with hormonal therapy for patients with ER-positive, HER2-negative breast cancer who have a high risk of the cancer returning.

  • PAM50 (Prosigna™). This test uses information from 50 genes to predict if a cancer will metastasize.

  • Additional tests. Other tests are being researched and may become additional tools to guide treatment options in the future.

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 is 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.