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What to Know: The CAP and ASCO Guideline on Estrogen and Progesterone Receptor Testing for Breast Cancer

To help doctors give their patients the best possible care, the College of American Pathologists and the American Society of Clinical Oncology (ASCO) developed evidence-based recommendations to improve the accuracy of testing for estrogen and progesterone receptors for breast cancer. This guide for patients is based on CAP’s and ASCO’s recommendations.

Key Points:

  • Estrogen and progesterone receptors are found in breast cancer cells that depend on estrogen and related hormones to grow.
  • All patients with invasive breast cancer or a breast cancer recurrence should have their tumors tested for estrogen and progesterone receptors.
  • This testing should be performed by an accredited laboratory that follows specific testing procedures and handles the samples in a consistent way.


About estrogen and progesterone receptors
Estrogen receptors (ER) and progesterone receptors (PR; also called PgR) may be found in breast cancer cells. Cancer cells with these receptors depend on estrogen and related hormones, such as progesterone, to grow. Estrogen and progesterone influence many hormonal functions in women, such as breast development.

If breast cancer cells have estrogen receptors, the cancer is called ER-positive breast cancer. If breast cancer cells have progesterone receptors, the cancer is called PgR-positive breast cancer. If the cells do not have either of these two receptors, the cancer is called ER/ PgR-negative. About two-thirds of breast cancers are ER and/or PgR positive.

About hormone therapy
Learning whether a tumor has estrogen and/or progesterone receptors helps doctors determine a patient’s risk of recurrence (return of the cancer after treatment) and whether the cancer can be treated with hormone therapy. Hormone therapy blocks the tumor from using estrogen and/or progesterone for cancers that are ER and/or PgR positive, slowing or stopping tumor growth. Two types of drugs may be used; one type called tamoxifen can be used for women of all ages, while other types of drugs called aromatase inhibitors (AIs) stop tissues and organs other than the ovaries from producing estrogen. AIs must never be used alone for women who have not gone through menopause.

For women who have not gone through menopause, hormone therapy for ER and/or PgR positive tumors may include stopping the production of estrogen and progesterone in the ovaries with surgery or injections.

Testing estrogen and progesterone receptors
Testing the tumor for both estrogen and progesterone receptors is a standard part of a breast cancer diagnosis. Because the results are used to guide treatment, it’s important that the results be accurate. The most common method currently used to test a tumor for estrogen and progesterone receptors is called immunohistochemistry or IHC. IHC testing can detect estrogen and progesterone receptors in cancer cells from a sample of tissue. This tissue may come from a biopsy (removal of a small amount of tissue for examination under a microscope), or from the surgery to remove all of the tumor and some or all of the breast.

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

  • The ER and PgR status should be tested on the primary tumor and/or areas of spread (called metastases) for each patient newly diagnosed with invasive breast cancer or a breast cancer recurrence.
  • A tumor is ER and/or PgR positive if at least 1% of the cells examined have estrogen and/or progesterone receptors, and for such a tumor, patients should talk with their doctors about considering hormone therapy.
  • Testing is best done on larger tissue samples. If the cancer has spread, testing on those areas may be considered as well.
  • Laboratories testing for ER and PgR should be accredited by the CAP or meet the additional accreditation requirements in the guideline and show agreement with other validated ER and PgR tests for both positive and negative results. The laboratory must also be inspected every two years to be sure that the testing methods conform to the guideline requirements.

What This Means for Patients
Because the results of ER and PgR testing can make a difference in a patient’s treatment and chance of recurrence, it’s important that these tests are accurate. This guideline was developed to help both doctors and laboratories know how to improve the accuracy of ER and PgR testing for patients with breast cancer. Understanding the ER/PgR status of the primary tumor and any recurrent tumors can help doctors make sure that patients receive the appropriate treatment and avoid side effects of a treatment that may not work. Use this guideline to talk with your doctor about the accuracy of your ER and PgR test results and what that means for your treatment.

Role of the Pathologist in Determining the ER/PgR Status
A pathologist is a doctor who examines tissues and cells to identify and diagnose disease. The pathologist examines biopsy specimens, along with other tests if necessary, to make a breast cancer diagnosis.

A biopsy is the most widely used method for making a firm diagnosis of breast cancer. During a biopsy procedure, in most instances, a surgeon removes small section of cells or tissues from the suspicious area for the pathologist to examine more closely in the laboratory.

The biopsy sample is tested for the presence of estrogen and progesterone receptors. Women with cancers containing these receptors are more likely to respond positively to hormonal therapy, like tamoxifen and aromatase inhibitors. The new ER/PgR testing guideline addresses the specific ways in which the tissues should be processed and the tests should be interpreted, which allows the pathologist to make a more accurate diagnosis and deliver better patient care.

Questions to Ask Your Doctor
To learn more about estrogen and progesterone receptor testing for breast cancer, consider asking your doctor the following questions:

  • What are the results of the ER and PgR tests on my tumor sample? What do they mean?
  • Does this laboratory meet the standard guidelines like those from the CAP and ASCO?
  • Is a board-certified pathologist on my treatment team?
  • Do you know if this is an experienced lab and if my tissue was quickly given to the pathologist after my biopsy or surgery as recommended by the guideline?
  • Can I obtain a copy of my pathology report (laboratory test results)?
  • Is my ER and PgR status indicated on the pathology report? Was the CAP-ASCO guideline recommendation used to define the status?
  • Based on these test results, what treatments do you recommend and why?
  • What are the possible side effects of these treatments?

Helpful Links
Read an abridged version of the clinical practice guideline published in the April 19, 2010, issue of Archives of Pathology & Laboratory Medicine.

Read an abridged version of the clinical practice guideline in the April 19, 2010, issue of the Journal of Clinical Oncology.

Cancer.Net Guide to Breast Cancer

Susan G. Komen for the Cure

To find a CAP-accredited laboratory in your community, visit the College’s Accredited Laboratory Directory.

About ASCO’s Guidelines
To help doctors give their patients the best possible care, the CAP and ASCO ask its medical experts to develop evidence-based recommendations for specific areas of cancer care, called clinical practice guidelines. Due to the rapid flow of scientific information in oncology, new evidence may have emerged since the time a guideline or assessment was submitted for publication. As a result, guidelines and guideline summaries, like this one, may not reflect the most recent evidence. Because the treatment options for every patient are different, guidelines are voluntary and are not meant to replace your physician’s independent judgment. The decisions you and your doctor make will be based on your individual circumstances. These recommendations may not apply in the context of clinical trials.

The information in this guide is not intended as medical or legal advice, or as a substitute for consultation with a physician or other licensed health care provider. Patients with health care-related questions should call or see their physician or other health care provider promptly and should not disregard professional medical advice, or delay seeking it, because of information encountered in this guide. The mention of any product, service, or treatment in this guide should not be construed as a CAP endorsement. The CAP is not responsible for any injury or damage to persons or property arising out of or related to any use of this patient guide, or to any errors or omissions.

Good cancer care starts with good cancer information. Well-informed patients are their own best advocates, and invaluable partners for physicians. Cancer.Net brings the expertise and resources of ASCO, the voice of the world’s cancer physicians, to people living with cancer and those who care for and care about them. ASCO is composed of more than 28,000 oncologists globally who are the leaders in advancing cancer care. All the information and content on Cancer.Net was developed and approved by the cancer doctors who are members of ASCO, making Cancer.Net the most up-to-date and trusted resource for cancer information on the Internet. Cancer.Net is supported by The ASCO Cancer Foundation, which provides funding for cutting-edge cancer research, professional education, and patient and family support.

Visit Cancer.Net to find guides on more than 120 types of cancer and cancer-related syndromes, clinical trials information, coping resources, information on managing side effects, medical illustrations, cancer information in Spanish, podcasts, the latest cancer news, and much more. For more information about ASCO’s patient information resources, call toll free 888-651-3038.

About CAP
CAP is a medical society serving more than 17,000 physician members and the laboratory community throughout the world. It is the world's largest association composed exclusively of board-certified pathologists and is widely considered the leader in laboratory quality assurance. The CAP is an advocate for high-quality and cost-effective medical care. Archives of Pathology & Laboratory Medicine, the leading peer-reviewed medical journal for pathologists worldwide, is published by the College.

The CAP developed to provide accurate and credible information to patients diagnosed with cancer and their loved ones to help them better understand their disease. The website includes information on more than 40 of the most common cancers and cancer-related illnesses in easy-to-understand language. The site also offers survivor stories, a comprehensive glossary of terms, and tips on how to read a surgical pathology report.

In addition, the College created, an email reminder website, 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 donations. The site also provides preventive patient information, developed by pathologists, on these diseases. For more information, contact




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