Estrogen receptor (ER)


The estrogen receptor (ER) is a special type of protein found inside certain cells throughout the body. It belongs to a family of proteins known as nuclear hormone receptors, which control how cells respond to hormones. Specifically, estrogen receptors respond to the hormone estrogen, which plays a key role in many important functions within the body.

There are two main types of estrogen receptors:

  • ERα (alpha)

  • ERβ (beta)

Normally, estrogen receptors are located in the cell’s nucleus, where they help control cell activities by turning specific genes on or off.

Where are estrogen receptors normally found?

Estrogen receptors are typically present in tissues that naturally respond to estrogen, such as:

  • Breasts

  • Uterus (endometrium)

  • Ovaries

  • Bones

  • Heart

  • Brain

Estrogen helps regulate essential functions in these tissues, including reproductive health, menstrual cycles, bone strength, heart health, and brain function.

How do pathologists test for estrogen receptors?

Pathologists use immunohistochemistry (IHC) to check for the presence of estrogen receptors in tissue samples. During this test, special antibodies specifically designed to attach to estrogen receptors are applied to the tissue sample. If estrogen receptors are present, the antibodies bind to them and produce a visible color change when viewed under a microscope.

Pathologists carefully examine the tissue, looking for this staining pattern specifically within the cell’s nucleus. The test results are reported as:

  • Positive: Estrogen receptors are present.

  • Negative: Estrogen receptors are absent.

Additionally, the pathology report typically includes more detailed information, such as:

  • The percentage of cells expressing estrogen receptors.

  • The strength (intensity) of the staining.

For example, a pathology report might say: “80% of tumour cells are ER-positive with strong staining intensity.”

This detailed information helps doctors predict the tumor’s behavior and decide on the most appropriate treatment.

What types of tumours express estrogen receptors?

Both benign (non-cancerous) and malignant (cancerous) tumours can express estrogen receptors, particularly if they originate from tissues that normally respond to estrogen.

Examples include:

Benign tumours
  • Fibroadenomas
Malignant tumours
  • Breast cancer
  • Uterine (endometrial) cancer
  • Certain types of ovarian cancer

Why is testing for estrogen receptors important?

Testing tumour tissue for estrogen receptors provides valuable information about how the cancer may behave and guides treatment decisions. ER-positive cancers typically:

  • Grow more slowly.

  • Have a better outlook (prognosis).

  • Often respond well to hormone-blocking therapies (such as tamoxifen or aromatase inhibitors), which either reduce estrogen levels or block its effects on tumour cells.

Identifying whether a cancer is estrogen receptor-positive helps pathologists and doctors select the most effective treatments tailored specifically to each patient.

Questions to ask your doctor

If your pathology report includes information about estrogen receptor status, consider asking your doctor:

  • Is my tumour estrogen receptor-positive or negative?

  • How does estrogen receptor status affect my prognosis or treatment options?

  • Which specific treatments are recommended based on my ER test results?

  • Do I need additional tests or monitoring related to hormone receptors?

Understanding the role of the estrogen receptor helps you become actively involved in your healthcare decisions and clearly understand your diagnosis and treatment options.

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