Estrogen and Progesterone Receptor Testing for Breast Cancer

Updated on: January 13, 2020

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 guidelines 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 2020 updated recommendations.

Key Points:

  • Estrogen and progesterone receptors are found in breast cancer cells that depend on estrogen and related hormones to grow.

  • All patients diagnosed with invasive breast cancer or a breast cancer recurrence should have their tumors tested for estrogen and progesterone receptors.

  • 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 sexual development, pregnancy, childbirth, and menopause.

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 2 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 person’s risk of recurrence, which is when cancer comes back after treatment, and whether the cancer can be treated with hormone therapy. Hormone therapy blocks ER-positive and/or PR-positive tumors from using estrogen and/or progesterone, which slows or stops tumor growth. Two types of drugs may be used: 1 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-positive and/or PR-positive tumors may include stopping the production of estrogen and progesterone in the ovaries through 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 are 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, which is the removal of a small amount of tissue for examination under a microscope, or from 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 everyone newly diagnosed with invasive breast cancer or a breast cancer recurrence. For those with ductal carcinoma in situ (DCIS), testing for ER status is recommended to find out if hormone therapy may reduce the risk of future breast cancer. Testing DCIS for PR status is considered optional.

  • 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 2 years to be sure that the testing methods follow the guideline requirements.

What This Means for Patients

Because the results of ER and PR testing can make a difference in a person’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 those with breast cancer. Understanding the ER/PR status of the primary tumor and any distant or 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?

  • Has a board-certified pathologist diagnosed my cancer?

  • 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

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.


The best cancer care starts with the best cancer information. With nearly 45,000 members who are leaders in advancing cancer care, the American Society of Clinical Oncology (ASCO) is the voice of the world’s cancer physicians. ASCO’s patient information website—Cancer.Net (—brings the expertise and resources of ASCO to people living with cancer and those who care for and care about them. Well-informed patients are their own best advocates and invaluable partners for physicians. Cancer.Net provides timely, comprehensive information to help patients and families make informed health care decisions. Cancer.Net is supported by Conquer Cancer®, The ASCO Foundation.

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

The College of American Pathologists (CAP), the leading organization of board-certified pathologists, serves patients, pathologists, and the public by fostering and advocating excellence in the practice of pathology and laboratory medicine worldwide.