College of American Pathologists
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HER2 Testing for Breast Cancer

Page published December 11, 2006

To help provide patients with the best possible care, the College of American Pathologists (CAP) seeks recommendations from experts in pathology to address specific areas of cancer testing. One such recommendation, the “HER2 Testing Guideline Recommendation,” was recently developed and released jointly by the College of American Pathologists and the American Society of Clinical Oncology (ASCO). The new clinical practice guideline focuses on human epidermal growth receptor-2 (HER2) testing for breast cancer. This patient guide is based on their recommendations.

As you read this guide, please keep in mind that every person treated for cancer is different. These recommendations are not meant to replace your or your doctors’ judgment. The final decisions you and your doctors make will be based on your individual circumstances.

Information in these patient education materials is not intended as medical advice or as a substitute for your treating doctor’s own professional judgment; nor does it imply either CAP’s endorsement of any specific product, service, or company.

Background Background

HER2 is a receptor (specialized protein) on the surface of breast cells and breast cancer cells that controls cancer cell growth, invasion, and spread of the cancer to other parts of the body. Every healthy breast cell has two copies of the HER2 gene, which controls production of the HER2 protein. High levels of the HER2 gene and/or protein occur in approximately 20 percent of patients with breast cancer. These tumors, referred to as HER2-positive, tend to be higher risk cancers, and often respond differently to some types of treatment, such as certain types of chemotherapy or hormonal treatments.

A new class of anticancer drugs specifically blocks HER2 to stop the growth of cancer cells. One of these drugs, trastuzumab (Herceptin), is approved by the U.S. Food and Drug Administration (FDA) to treat HER2-positive breast cancer. Trastuzumab has shown to be effective against HER2-positive cancers. However, this drug is costly and causes serious side effects (especially heart weakness) in a small number of patients. Therefore, it is important to accurately determine the HER2 status of each patient’s breast cancer to make sure that the patients most likely to be helped (those with HER2-positive cancer) are offered the drug, and those unlikely to be helped (those with HER2-negative cancer) can avoid potential side effects.

The two FDA-approved methods currently used in the United States to test for HER2 are immunohistochemistry (IHC) and fluorescence in-situ hybridization (FISH). IHC testing can show how much of the HER2 protein is present on the tumor cell surface, while FISH testing measures the number of copies of the HER2 gene inside each cell.

Recommendations Recommendations

To improve the accuracy of HER2 testing, CAP and ASCO recommend the following:

  • The HER2 status should be determined for each patient with invasive breast cancer.

  • IHC and FISH tests are the only FDA-approved methods for HER2 testing. Either test may be used, as long as it is correctly performed, validated, and reproducible.

  • The values for positive and negative test results must be clearly defined. A positive test result means that the tumor has high levels of the HER2 protein or an increased number of gene copies, while a negative test result means that the tumor does not. Test results that are not clearly positive or negative should be called “equivocal,” which requires a repeat of the test and/or the use of a different test for further evaluation.

  • The pathology laboratories that perform HER2 testing should follow specific testing procedures and handle tissue samples consistently.

  • The pathology laboratories that perform HER2 testing are required to show 95 percent concordance (agreement) with another validated HER2 test for both positive and negative results, participate in ongoing internal and external quality assurance procedures, and hold current accreditation by a valid accrediting agency. (All accredited laboratories undergo an onsite inspection once every two years, participate in ongoing quality assurance activities, and have a valid Clinical Laboratory Improvement Act (CLIA) certificate or equivalent state license if the laboratory operates in New York or Washington state).

What This Means for Patients What This Means for Patients

Because the results of HER2 testing make a difference in the treatment and outcome a patient receives, it is important that HER2 testing produces accurate results. This guideline was developed to enhance the accuracy of HER2 testing for patients with breast cancer. Use this guideline to talk with your doctor about the accuracy of your test results for HER2 in the laboratory that he or she uses.

Questions to Ask the Doctor Questions to Ask the Doctor

To learn more about HER2 testing for breast cancer, consider asking your doctor the following questions:

  • Which test was done on my tumor, IHC or FISH?

  • What are the results of the HER2 test on my tumor sample? What do they mean?

  • Is the lab accredited in accordance with the CAP/ASCO guidelines?

  • Can I obtain a copy of my pathology report?

  • Is my HER2 status indicated on the pathology report?

  • Based on these test results, what treatments do you recommend? Why do you believe these are the best options for this type of cancer? What are the possible side effects of these treatments?

Helpful Links Helpful Links

Read the entire clinical practice guideline published in the January 1, 2007 Archives of Pathology and Laboratory Medicine.

For more information, contact the CAP at 800-323-4040 ext. 7439.

Resources Resources

American Cancer Society
1599 Clifton Rd., NE
Atlanta, GA  30329-4251
Toll Free: 800-ACS-2345 (800-227-2345)
TTY: 866-288-4327
Phone: 404-320-3333
111 Forrest Ave., #112
Narberth, PA  19702

275 Seventh Ave.
New York, NY  10001
Toll Free: 800-813-HOPE (800-813-4673)
Phone: 212-712-8400

HER2 Support Group
6973 Mimosa Dr.
Carlsbad, CA   92009
Phone: 760-602-9178

National Cancer Institute
Public Inquiries Office
Building 31, Rm. 10A31
31 Center Dr., MSC 2580
Bethesda, MD  20892-2580
Toll Free: 800-4-CANCER (800-422-6237)
TTY: 800-332-8615
Phone: 301-435-3848

The Susan G. Komen Breast Cancer Foundation
5005 LBJ Freeway, Ste. 250
Dallas, TX  75244  
Toll Free: 800-IM-AWARE (800-462-9273)
Phone: 972-855-1600

Y-ME National Breast Cancer Organization, Inc.
212 W Van Buren, Ste. 1000
Chicago, IL  60607
Toll Free: 800-221-2141 (English)
Toll Free: 800-986-9505 (Spanish)
Phone: 312-986-8338

Young Survival Coalition
61 Broadway, Ste. 2235
New York, NY  10006
Phone: 646-257-3000

About CAP About CAP

The CAP is a medical society that serves nearly 16,000 physician members and the laboratory community throughout the world. It is the world's largest association composed exclusively of pathologists and is widely considered the leader in laboratory quality assurance. The College is an advocate for high-quality and cost-effective medical care. Archives of Pathology and Laboratory Medicine, the leading peer-reviewed medical journal for pathologists worldwide, is published by the College.

The College also produces, an e-mail reminder web site, to help patients remember to schedule their life-saving health tests such as mammograms, Pap tests, colon cancer screenings, diabetes screenings, cholesterol testing, and to schedule their next blood donation. The site also provides preventive patient information, developed by pathologists, on these diseases. For more information, contact CAP at 800-323-4040 ext. 7439.

About ASCO About ASCO

ASCO is the world’s leading professional organization representing physicians of all oncology subspecialties who care for people with cancer. ASCO’s more than 20,000 members from the United States and abroad set the standard for patient care and lead the efforts to discover more effective cancer treatments, increase funding for clinical and translational research, and, ultimately, improve cancer care for the estimated 10 million people diagnosed with cancer worldwide each year. ASCO publishes the Journal of Clinical Oncology (JCO), the preeminent, peer-reviewed, medical journal on clinical cancer research, and produces People Living With Cancer (, a comprehensive consumer website providing oncologist-vetted cancer information to help patients and families make informed health-care decisions.

For permissions information, contact

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