Estrogen and Progesterone Receptor Testing for Breast Cancer

April 19, 2010

To help doctors give their patients the best possible care, the American Society of Clinical Oncology (ASCO) and the College of American Pathologists (CAP) 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 ASCO's and CAP'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 PR-positive breast cancer. If the cells do not have either of these two receptors, the cancer is called ER/PR-negative. About two-thirds of breast cancers are ER and/or PR 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 PR positive, slowing or stopping tumor growth. Two types of drugs may be used; one type called tamoxifen (Nolvadex) 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 PR 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 PR testing, ASCO and the CAP recommend the following:

  • The ER and PR 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 PR 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 PR should be accredited by the CAP or meet the additional accreditation requirements in the guideline and show agreement with other validated ER and PR 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 PR 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 PR testing for patients with breast cancer. Understanding the ER/PR 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 PR test results and what that means for your treatment.

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 PR tests on my tumor sample? What do they mean?
  • Does this laboratory meet the standard guidelines like those from ASCO and the CAP?
  • 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 guidelines?
  • Can I obtain a copy of my pathology report (laboratory test results)?
  • Is my ER and PR status indicated on the pathology report? Was the ASCO-CAP 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 the entire clinical practice guideline published in the Journal of Clinical Oncology at

Cancer.Net Guide to Breast Cancer

What to Know: ASCO's Guideline on Hormonal Therapy for Hormone Receptor-Positive Breast Cancer

About ASCO's Guidelines

To help doctors give their patients the best possible care, ASCO asks 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 an ASCO endorsement. ASCO 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.

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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.