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Doctors use many tests to diagnose cancer and find out if it has spread to other parts of the body beyond the breast. Some tests may also help the doctor decide which treatments may be the most effective. For most types of cancer, a biopsy (the removal of a small amount of tissue for examination under a microscope) is the only way to make a definitive diagnosis of cancer. If a biopsy is not possible, the doctor may suggest other tests that will help make a diagnosis. Imaging tests may be used to find out whether the cancer has metastasized. Your doctor may consider these factors when choosing a diagnostic test:
- Age and medical condition
- Type of cancer suspected
- Severity of symptoms
- Previous test results
The diagnosis of breast cancer usually begins when a woman or her doctor discover a mass or abnormal calcification on a screening mammogram, or an abnormality in the woman’s breast by clinical or self-examination. Several tests are usually performed to confirm a diagnosis of breast cancer.
The following tests may be used to diagnose breast cancer or for follow-up testing after the cancer has been diagnosed. Not every person will have all of these tests, and some imaging tests are not recommended if there are no signs that the cancer has spread.
Diagnostic mammography. Diagnostic mammography is similar to screening mammography except that more views (pictures) of the breast are taken, and it is often used when a woman is experiencing signs, such as nipple discharge or a new lump. Diagnostic mammography may also be used if something suspicious is found on a screening mammogram.
Ultrasound. An ultrasound uses high-frequency sound waves to create an image 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. Ultrasounds are not used for screening.
MRI. An MRI uses magnetic fields, not x-rays, to produce detailed images of the body. A contrast medium (a special dye) is injected into a patient’s vein to create a clearer picture of the breast. A breast MRI may be used once 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. It may also be used for screening, particularly along with mammography for some women with a high risk of breast cancer (see Prevention).
Biopsy. 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. The sample removed during the biopsy is analyzed by a pathologist. There are different types of biopsies, classified by the technique and/or size of needle used to collect the tissue sample.
- A fine needle aspiration biopsy uses a thin needle to remove a small sample of cells.
- A core needle biopsy uses a thicker 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. A vacuum-assisted biopsy removes several large cores of tissue. Local anesthesia (medication to block the awareness of pain) is used to lessen a patient’s discomfort.
- Image-guided biopsy is used when a distinct lump can't be felt, but an abnormality is seen with an imaging test, such as a mammogram. 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. 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, in order to help find the best location.
- A surgical biopsy removes the largest amount of tissue. This biopsy may be incisional (removal of part of the lump) or excisional (removal of the entire lump). Because definitive 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 biopsies are recommended to diagnose breast cancer. This means that only one surgical procedure is needed to remove the tumor and to take samples of the lymph nodes.
If cancer is diagnosed, surgery is needed to remove the cancer in the breast and evaluate the lymph nodes for cancer (called a sentinel lymph node biopsy; see Treatment), although treatment may be given first (called neoadjuvant therapy, see Treatment). The goal is to achieve clear surgical margins (no cancer cells at the edge of the tissue removed during surgery). If there is cancer in the lymph nodes, the cancer is called lymph node-positive breast cancer (or node-positive, for short); if there is no cancer in the lymph nodes, the cancer is called lymph node-negative breast cancer (or node-negative, for short). More information about lymph node evaluation can be found in Staging.
Tumor features. Examination of the tumor under the microscope determines if it is invasive or in situ; ductal or lobular; the grade (how different the cancer cells look from healthy cells); and whether the cancer has spread to the lymph nodes. The margins (edges) of the tumor are also examined and their distance from the tumor is measured.
Molecular testing of the tumor
Your doctor may recommend additional laboratory tests on your tumor sample to identify specific genes, proteins, and other factors unique to the tumor. Results of these tests will help your doctor recommend treatment.
Estrogen receptor (ER) and progesterone receptor (PR) tests. Breast cancer cells with these receptors depend on the hormones estrogen and/or progesterone to grow. The presence of these receptors helps determine both the patient’s risk of recurrence and the type of treatment will be most likely to prevent recurrence. Generally, hormonal therapy (see Treatment) works well for ER-positive or PR-positive tumors, but chemotherapy is also used in specific situations. About 75% to 80% of breast cancers have estrogen and/or progesterone receptors. Learn about ER and PR testing recommendations from ASCO and the College of American Pathologists (CAP).
HER2 tests. About 20% to 25% of breast cancers have an increase in the number of copies of a gene called the human epidermal growth factor receptor (HER2). This is called HER2-positive cancer. The gene makes a protein which is found on the cancer cell and is important in tumor cell growth; these types of cancers usually grow more quickly. The HER2 status helps determine whether a certain type of drug, such as trastuzumab (Herceptin), lapatinib (Tykerb), pertuzumab (Perjeta), or trastuzumab emtansine (TDM-1) might help treat the cancer. In addition, about 50% of HER2-positive tumors also have other positive hormone receptors and can benefit from both types of therapy. Read ASCO’s and CAP's recommendations for HER2 testing for breast cancer.
If a person’s tumor does not have ER, PR, and/or HER2, the tumor is called triple-negative. Triple-negative breast cancers make up about 15% of invasive breast cancers and are the most common type diagnosed in women with BRCA1 mutations. This type of breast cancer usually grows and spreads more quickly. Triple-negative breast cancer seems to be more common among younger women, particularly younger black women.
Ki67. How quickly a cell divides into two cells, called tumor proliferation, can be measured in a tumor sample and is referred to as Ki67 or MIB1. How well chemotherapy works to treat a tumor has been linked with how quickly tumor cells grow and divide. Chemotherapy seems to work best for tumors cells that grow more quickly and hormonal therapy tends to work better for slower growing cancers. Ki67 is not used in many hospitals because the results depend on the laboratory doing the testing or how the testing is done. However, there has been interest in standardizing the testing methods so measuring tumor proliferation is becoming more common.
Genetic testing of the tumor. Tests that look at the biology of the tumor are commonly used to understand more about a woman’s breast cancer, particularly for cancers that have not spread to other organs. The tests below look at the genes in the tumor sample (not a person’s inherited genes) to help predict the risk of cancer recurrence, and to help choose treatment. They are usually done after surgery (see Treatment). A person with a higher risk of recurrence will likely need chemotherapy, while a person with a lower risk of recurrence can possibly avoid these treatments and their potential side effects. For more information about genetic tests, what they mean, and how the results might affect your treatment plan, talk with your doctor.
- Oncotype Dx™ (the recurrence score) is a test that evaluates 16 cancer-related genes and five reference genes to estimate the risk of distant recurrence (return of the cancer in a place other than the breast) within 10 years after diagnosis for women with stage I or stage II (see Staging), node-negative, ER-positive breast cancer treated with hormonal therapy alone. It is mainly used to help make decisions about whether chemotherapy should be added to a person’s treatment. Recent research suggests that this test might be useful to decide about use of chemotherapy in node-positive disease in some situations.
- Mammaprint™ is another, similar test using information about 70 genes to predict the risk of the cancer coming back for early-stage, low-risk breast cancer. It is approved by the U.S. Food and Drug Administration (FDA) for estimating the risk of recurrence in early-stage breast cancer, but has not been studied specifically as a way to predict if chemotherapy will work.
The doctor may also need to do several types of blood tests to learn more about the cancer:
Serum chemistry. These tests are often done to look at blood electrolytes (minerals in your body, such as potassium and calcium) and enzymes (specialized proteins) that can be abnormal if cancer has spread. However, many noncancerous conditions can cause changes in these tests, and they are not specific to cancer.
- Alkaline phosphatase is an enzyme that can be associated with disease that has spread to the liver, bone, or bile ducts.
- Blood calcium levels can be high if cancer has spread to the bone.
- Total bilirubin count and the enzymes alanine aminotransferase (ALT) and aspartate aminotransferase (AST) evaluate liver function. High levels of any of these substances can indicate liver damage, a sign that the cancer may have spread to that organ.
Blood tumor marker tests. A serum tumor marker (also called a biomarker) are proteins found in a person's blood that can be associated with cancer. High levels of a serum tumor marker may be due to cancer or a noncancerous condition. Tumor marker testing is not recommended for early-stage breast cancer (and the markers are not usually high), but they may be useful to monitor recurrent or metastatic disease. Learn more about tumor markers for breast cancer.
The doctor may recommend additional tests (depending on the patient’s medical history, symptoms, how much the disease has grown in the breast and lymph nodes, and the results of the physical examination) to evaluate the stage of the cancer. Read Staging for more information. Many of these tests may not be done until after surgery. These tests are generally only recommended for patients with later stage disease.
- 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.
- A bone scan may be used to look for spread to the bones. A bone 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 gray to the camera, and areas of injury, such as those caused by cancer, appear dark. Some cancers may not show up on bone scan.
- A computed tomography (CT or CAT) 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 creates a three-dimensional picture of the inside of the body with an x-ray machine. A computer combines these images into a detailed, cross-sectional view that shows any abnormalities or tumors. Sometimes, a contrast medium is injected into a patient’s vein to provide better detail.
- A positron emission tomography (PET) scan may be used to find out whether the cancer has spread to organs outside of the breast. A PET scan is a way to create pictures of organs and tissues inside the body. A small amount of radioactive sugar (glucose) is injected into a patient’s body. This substance is absorbed more by organs and tissues that use the most energy. Because cancer tends to use energy actively (called metabolically active), it absorbs more of the radioactive substance. A scanner then detects this substance to produce images of the inside of the body. A combination PET/CT scan may also be used to better understand if metabolically active areas could be cancer.
Learn more about what to expect when having common tests, procedures, and scans.
After these diagnostic tests are done, 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. Learn more about the first steps to take after a diagnosis of cancer.