Diagnosis

Doctors use many tests to diagnose cancer and determine if it has metastasized. Some tests may also find out 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
  
  
• The type of cancer suspected
  
  
• Severity of symptoms
  
  
• Previous test results

The diagnosis of breast cancer usually begins when a woman or her doctor discovers a mass or abnormal calcification (tiny spot of calcium usually found on an x-ray) on a screening mammogram, or an abnormality in the woman’s breast by clinical examination or self-examination. Several tests may be done to confirm a diagnosis of breast cancer. Not every person will have all of these tests.

In addition to screening mammography, the following tests may be used to diagnose breast cancer:

Imaging tests

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 may 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 contrast medium (a special dye) may be injected into a patient’s vein to create a clearer picture.

An MRI may be used once a woman has been diagnosed with cancer to check the other breast for cancer, but the benefit of this is questionable. It may also be used for screening. According to the ACS, women at high risk for breast cancer (for example, women with BRCA gene mutations or a strong family history of breast cancer) should receive MRI screening along with a mammogram. MRI is often better than mammography and ultrasound at finding a small mass in a woman’s breast, especially for women with very dense breast tissue. However, an MRI has the risk of having a higher rate of false-positive test results (a test result that indicates cancer when there is no cancer present) and may result in more biopsies and other tests. In addition, an MRI does not show calcifications, which could indicate in situ breast cancer (DCIS). Talk with your doctor for more information.

Surgical tests

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 from the biopsy is analyzed by a pathologist (a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease). A biopsy is specified by the technique and/or size of needle used to collect the tissue sample.

• A fine needle aspiration biopsy (FNAB) uses a small needle to remove a small sample of cells.
  
  
• A core needle biopsy uses a larger needle to remove a larger sample of tissue. This is usually the preferred biopsy technique for determining whether a physical exam or imaging finding is cancer. A vacuum-assisted biopsy removes multiple large cores of tissue.
  
  
• 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 optimally done after a cancer diagnosis has been made, a surgical biopsy is usually not the recommended approach to determining whether an abnormality is cancerous. If a surgical biopsy confirms cancer, then further surgery is usually required to remove remaining cancer in the breast and evaluate the lymph nodes. Therefore, in order to keep surgery to one operation, it’s best when a patient receives a core biopsy to diagnose the cancer, followed by the type of cancer surgery with the best chance at removing all of the disease, as determined by the doctor.
  
  
• Image-guided biopsy is used when a distinct lump can't be felt, but an abnormality is seen on a radiologic image, such as a mammogram. During this procedure, a needle is guided to the area of concern with the help of mammography, ultrasound, or MRI. A stereotactic biopsy is performed with mammography guidance. A small metal clip may be put into the breast to mark the site of biopsy, in case the sample tissue proves cancerous and additional surgery is required. An image-guided biopsy can be done using a fine needle, core, or vacuum-assisted biopsy, depending on the amount of tissue being removed.

If cancer is diagnosed, surgery is needed to remove the cancer in the breast and evaluate the lymph nodes for the presence of cancer (discussed in Treatment). The goal is to achieve clear surgical margins (no cancer cells at the edge of the tissue removed during surgery). If lymph nodes show evidence of cancer, the cancer is called lymph node-positive breast cancer (or node-positive, for short); if the lymph nodes do not show evidence of cancer, the cancer is called lymph node-negative breast cancer (or node-negative, for short). Additional information about lymph node evaluation can be found in Staging.

Testing the tissue

The pathologist tests the tissue from the biopsy and the surgery for the following to help guide treatment decisions

Tumor features. Examination of the tumor under the microscope determines if it is invasive or in situ; ductal or lobular; 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.

Estrogen receptor (ER) and progesterone receptor (PR) tests. Breast cancer cells with these receptors depend on the hormones estrogen and progesterone to grow. The presence of these receptors helps determine both the patient’s prognosis (chance of recovery) and whether the cells are likely to respond to hormone therapy. Generally, ER-positive or PR-positive tumors respond to hormone therapy. About 75% to 80% of breast cancers express estrogen and/or progesterone receptors.

HER2 tests. There is too much of the protein called human epidermal growth factor receptor two (HER2) in about 20% to 25% of invasive breast cancers, and this type of cancer is called HER2-positive cancer. The HER2 status helps determine whether a drug, such as trastuzumab (Herceptin), might be useful for treating breast cancer. Read ASCO’s recommendations for HER2 testing for breast cancer.

If a person’s tumor does not have ER, PR, and HER2, the tumor is called triple-negative. Triple-negative breast cancers comprise about 15% of invasive breast cancers. This subtype of breast cancer is frequently more aggressive, and seems to be more common among black women and younger women diagnosed with breast cancer.

Testing a tumor’s genes

Tests that look at the biology of the tumor are becoming more common to understand more about a woman’s breast cancer. The tests below look at the expression of genes in a tumor sample to predict the risk of cancer recurrence. A person with a higher risk of recurrence will likely receive additional treatment, while a person with a lower risk of recurrence can avoid extra treatment and its possible side effects. For more information about these tests, what they mean, and how it might affect your treatment plan, talk with your doctor.

• Oncotype Dx is a test that evaluates 21 genes to estimate the risk of distant recurrence (return of the cancer in a place other than the breast) at 10 years for women with stage I or stage II (see Staging) node-negative, ER-positive breast cancer treated with hormone therapy alone. It is mainly used to help make decisions about whether chemotherapy should be added to a person’s treatment.
  
  
• Mammaprint is another, similar test using about 70 genes to predict the risk of the cancer coming back. It is approved in early-stage, low-risk breast cancer. Although it is approved by the U.S. Food and Drug Administration (FDA) for estimating the risk of recurrence in early-stage breast cancer, it requires a frozen sample of tumor, which is not how cancer samples are generally collected and stored in the United States, thereby limiting its use.

Blood tests

The doctor may also need to do blood tests to learn more about the cancer.

A serum chemistry panel is frequently done to evaluate blood electrolytes (minerals in your body, such as potassium and calcium) and enzymes (specialized proteins) that can be abnormal if cancer has spread. However, it is important to note that many noncancerous conditions can cause variations 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 elevated 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 signal of possible spread to that organ.

Blood tumor marker tests

A serum tumor marker (also called a biomarker) is a substance found in a person's blood that can be associated with the presence of cancer. An elevated serum tumor marker may indicate an abnormal process in the body, which could be due to cancer or a noncancerous condition. Tumor marker testing is not usually recommended in early-stage breast cancer, but these markers may be useful in the follow-up care of recurrent or metastatic disease. Common tumor marker assays in breast cancer include CA27.29, CA15-3, and CEA. Learn more about tumor markers for breast cancer.

Additional tests

The doctor may order additional tests (depending on the individual’s medical history and results of the physical examination) to evaluate the stage of the cancer. Read Staging for more information. These tests are generally only recommended for patients with more advanced stage disease.

• A chest x-ray may be used to look for cancer that has spread from the breast to the lung.
  
  
• 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.
  
  
• A computed tomography (CT or CAT) scan may be used to look for distant tumors. 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 determine whether the cancer has spread. A PET scan is a way to create pictures of organs and tissues inside the body. A small amount of a radioactive substance is injected into a patient’s body and absorbed by the organs or tissues being studied. This substance gives off energy that is detected by a scanner, which produces the images.

Learn more about what to expect when having common tests, procedures, and scans.

Find out more about common terms used during a diagnosis of cancer.