Estrogen receptor (ER) positive breast cancer

Find out what ER positive means, how it's diagnosed and how hormone receptor test results help guide breast cancer treatment.

Update Date: 26.08.2026

Overview
Symptoms
Causes
Risk factors
Complications
Prevention
Diagnosis
Treatment
Alternative medicine
Coping and support
Preparing for an appointment

Overview

Estrogen receptor (ER) positive breast cancer is the most common type of breast cancer. ER positive means that the cancer cells have proteins called estrogen receptors. The hormone estrogen can attach to these receptors and help the cancer grow.

After breast cancer is diagnosed, the cancer cells are tested for estrogen receptors (ERs), progesterone receptors (PRs) and a protein called HER2. The results help your healthcare team learn more about the cancer and choose treatments that are most likely to work.

Hormone therapy, also called endocrine therapy, is often an important part of treatment for ER positive breast cancer. Hormone therapy for breast cancer, can block the effects of estrogen on the cancer or lower estrogen levels in the body. This can slow or stop the cancer from growing.

Types

ER positive breast cancer is a type of hormone receptor (HR) positive breast cancer. HR positive means that cancer cells have receptors for estrogen, progesterone or both. ER, PR and HER2 test results provide important information about the cancer and help guide treatment.

ER positive and PR positive

Most ER positive breast cancers also are PR positive. This means the cancer cells have receptors for both estrogen and progesterone. Hormone therapy is often an important part of treatment for these cancers.

ER positive and PR negative

Some ER positive breast cancers are PR negative. This means the cancer cells have estrogen receptors but don't have progesterone receptors. Because the cancer is ER positive, hormone therapy may still be an important part of treatment.

ER low positive

Some ER positive breast cancers have estrogen receptors in only a small number of the cancer cells. This is called ER low positive breast cancer. ER low positive breast cancers are considered ER positive, but they may respond differently to hormone therapy. There is less evidence about how much hormone therapy helps with these cancers.

HER2 status

ER positive breast cancer can be HER2 positive or HER2 negative. HER2 is a protein that helps cells grow. Testing shows how much HER2 the cancer cells have and helps guide treatment.

  • ER positive, HER2-positive. These breast cancers have high levels of HER2 or extra copies of the HER2 gene. Medicines that target HER2 may be part of treatment.
  • ER positive, HER2 negative. These breast cancers don't have high levels of HER2. HER2 test results, along with other features of the cancer, help your healthcare team choose treatment.

Symptoms

Estrogen receptor (ER) positive breast cancer can have the same symptoms as other types of breast cancer. Many people with early-stage breast cancer don't have any symptoms.

When symptoms happen, they may include:

  • A new lump or thickened area in the breast or underarm.
  • A change in the size or shape of the breast.
  • Swelling of all or part of the breast.
  • Changes in the skin of the breast, such as dimpling, thickening, scaling or a change in skin color.
  • A nipple that turns inward or other changes in the nipple.
  • Nipple discharge, especially if it is bloody.
  • Breast or nipple pain that doesn't go away.

When to seek care

Make an appointment with a healthcare professional if you notice a new change or a change that isn't typical in your breast. Most breast changes aren't cancer, but it's important to have changes checked.

Don't wait for your next screening mammogram to have a breast change checked. Tell your healthcare team about a change even if a recent mammogram didn't find breast cancer. Your healthcare professional may recommend more tests to find out what's causing the change.

Causes

The exact cause of estrogen receptor (ER) positive breast cancer isn't known. Like other types of breast cancer, it starts when breast cells develop changes in their DNA. DNA contains the instructions that tell cells what to do. The changes cause the cells to grow and multiply when they shouldn't. Over time, these cells can form a tumor.

ER positive breast cancer cells have proteins called estrogen receptors. Estrogen can attach to these receptors and help the cancer grow.

Many factors can increase the risk of having breast cancer. But most people who get breast cancer don't have one clear cause.

Risk factors

A risk factor is something that increases the chance of getting breast cancer. Having one or more risk factors doesn't mean that you'll get estrogen receptor (ER) positive breast cancer. And some people who get breast cancer have no known risk factors.

Many risk factors linked to ER positive breast cancer also increase the risk of breast cancer in general.

Older age

The risk of breast cancer increases with age. Most breast cancers occur after age 50.

Hormone and reproductive factors

Some factors can increase how long breast tissue is exposed to estrogen. Longer exposure to estrogen is linked to a higher risk of breast cancer. These include:

  • Starting your period at a younger age.
  • Starting menopause at an older age.
  • Never having given birth.
  • Having your first child at an older age.

Menopausal hormone therapy

Taking menopausal hormone therapy can increase the risk of breast cancer. The risk is higher with treatment that contains both estrogen and progestin.

Inherited gene changes

Some gene changes passed from parents to children increase the risk of breast cancer. Certain inherited gene changes are more closely linked to ER positive breast cancer. One example is a change in the CHEK2 gene.

Other inherited gene changes, including changes in the BRCA1, BRCA2, ATM and CDH1 genes, increase the risk of breast cancer in general. Having an inherited gene change doesn't mean that you'll get breast cancer.

Family history

Having a blood relative with breast cancer increases your risk. Examples of blood relatives are parents, grandparents and cousins. The risk may be higher if more than one blood relative has had breast cancer or if a blood relative was diagnosed at a younger age.

Personal health history

Having had breast cancer increases the risk of developing another breast cancer. Certain breast conditions also increase the risk of breast cancer. These include atypical ductal hyperplasia, atypical lobular hyperplasia and lobular carcinoma in situ (LCIS).

Dense breasts

Having extremely dense breasts increases the risk of breast cancer. Dense breast tissue also can make breast cancer harder to see on a mammogram.

Excess weight after menopause

Having excess weight after menopause increases the risk of breast cancer.

Alcohol

Drinking alcohol increases the risk of breast cancer. The risk increases with the amount of alcohol you drink.

Not being physically active

Not getting enough physical activity is linked to a higher risk of breast cancer.

Radiation exposure

Having radiation therapy to the chest at a young age, such as to treat lymphoma, increases the risk of breast cancer later in life.

Complications

Complications can happen with estrogen receptor (ER) positive breast cancer. These include:

  • Cancer that comes back. ER positive breast cancer may come back after treatment. This is called recurrent breast cancer. It may come back in or near the breast or in another part of the body, such as the lungs, liver or bones. Cancer that comes back in another part of the body is called metastatic cancer.
  • Infertility. ER positive breast cancer treatment may include chemotherapy, which can make it harder to get pregnant after treatment. Not everyone with ER positive breast cancer needs chemotherapy. If you want to have children in the future, talk about this with your healthcare team before treatment starts. Your team may refer you to a fertility specialist who can explain your options. These options might include freezing eggs, freezing embryos and other ways to preserve fertility.
  • Lymphedema. Surgery or radiation therapy that affects the lymph nodes may cause lymphedema. Lymphedema is swelling caused by a buildup of fluid. It most often affects the arm on the side of the body where breast cancer was treated.

Prevention

There's no sure way to prevent estrogen receptor (ER) positive breast cancer. But there are things you can do that may lower your risk.

  • Ask about breast cancer screening. Talk with your healthcare professional about when to start screening. Your risk factors can help determine which screening tests you may need. If you have dense breasts and other risk factors, your healthcare professional may recommend a breast MRI in addition to a mammogram. Ask about the benefits and risks of each test. Together, you can decide which screening plan is right for you.

    Screening doesn't prevent breast cancer. But it may help find breast cancer early, when treatment is more likely to be successful.

  • Know what's typical for your breasts. You may choose to check your breasts sometimes to learn how they usually look and feel. This can make it easier to notice a new lump or other change. Tell your healthcare professional about any changes you notice.
  • Maintain a healthy weight. Having excess weight, especially after menopause, increases the risk of breast cancer. If you need help reaching or maintaining a healthy weight, talk with your healthcare professional.
  • Be physically active. Aim for at least 30 minutes of physical activity on most days of the week. If you haven't been active lately, start slowly and ask your healthcare professional for guidance.
  • Avoid or limit alcohol. Drinking alcohol increases the risk of breast cancer. The more alcohol you drink, the greater the risk. If you choose to drink alcohol, limit how much you drink.
  • Consider breastfeeding. If you have a baby, breastfeeding may lower the risk of breast cancer. Consider breastfeeding if you want to and are able to.

If you have a family history of breast cancer, talk with your healthcare team about your risk. Genetic counseling and genetic testing may help find inherited gene changes that increase the risk of breast cancer.

Some people at high risk of breast cancer may choose to take medicine to help lower their risk. Talk with your healthcare team about whether this may be an option for you.

Diagnosis

Diagnosing estrogen receptor (ER) positive breast cancer usually involves several steps. If you have breast symptoms or if a screening mammogram finds something that may be breast cancer, your healthcare team may recommend more testing. This may include a breast exam and imaging tests, such as a diagnostic mammogram or an ultrasound.

If these tests find a change that could be cancer, you may need a biopsy. During a biopsy, a healthcare professional removes a small sample of breast tissue. The sample goes to a lab to be checked for cancer.

If breast cancer is found, lab tests can tell whether the cancer cells have estrogen receptors (ERs). Cancer that has estrogen receptors is called ER positive breast cancer. Other tests give your healthcare team more information about the cancer and help guide treatment.

Breast exam

During a breast exam, a healthcare professional checks the breasts for lumps and other changes. This includes changes in the skin or nipple. The healthcare professional also feels for lumps around the armpits and collarbones.

Mammogram

A mammogram is an X-ray of the breast tissue. Mammograms are often used to screen for breast cancer. If a screening mammogram shows an area that needs a closer look, you may have a diagnostic mammogram. A diagnostic mammogram makes more-detailed images of the area.

Breast ultrasound

Ultrasound uses sound waves to make pictures of structures inside the body. A breast ultrasound can give your healthcare team more information about an area of concern. For example, it can show whether a breast lump is solid or filled with fluid.

Breast ultrasound also may be used to look at lymph nodes under the arm. If a lymph node looks like it could have cancer, your healthcare team may recommend a biopsy.

Breast MRI

Magnetic resonance imaging (MRI) uses a magnetic field and radio waves to create pictures of the inside of the body. Breast MRI makes detailed pictures of the breast. Your healthcare team may recommend breast MRI to look for other areas of cancer in the affected breast. It also may be used to look for cancer in the other breast.

Before breast MRI, you usually receive an injection of contrast material. The contrast material helps make the images clearer.

Biopsy

A breast biopsy is a procedure to remove breast tissue for testing in a lab. A healthcare professional places a needle through the skin and into the breast to remove the tissue. This is called a needle biopsy.

Mammography, ultrasound or MRI may be used to guide the needle to the area that needs testing. A small metal marker often is placed at the biopsy site. The marker can be seen on future imaging tests and helps your healthcare team find the area again.

Lab testing

The tissue sample taken during a biopsy is sent to a lab for testing. A doctor who specializes in looking at body tissue, called a pathologist, checks the tissue for cancer. If breast cancer is found, more tests provide information about the cancer and help guide treatment.

The test results are included in a pathology report. The report may include information about:

  • Cancer type. This describes where the breast cancer started. For example, breast cancer may start in a milk duct or in a breast gland called a lobule.
  • Tumor grade. The grade describes how different the cancer cells look from healthy cells. The grade can help show how quickly the cancer is likely to grow.
  • Hormone receptor status. Breast cancer cells are tested for estrogen receptors and progesterone receptors. Cancer cells that have estrogen receptors are called ER positive. Tests also can show how many of the cancer cells have estrogen receptors. The results help your healthcare team decide whether hormone therapy may be helpful.
  • HER2 status. Breast cancer cells also are tested for a protein called HER2. The results show how much HER2 the cancer cells make. This information helps your healthcare team decide whether treatments that target HER2 may be helpful.

Genomic tumor testing

If you have early-stage ER positive, HER2-negative breast cancer, your healthcare team may recommend genomic tumor testing. These tests look at the activity of certain genes in the cancer cells. The results can help show how likely the cancer is to come back. They also can help your healthcare team decide whether chemotherapy may be helpful along with hormone therapy.

Grades

Breast cancer grade describes how cancer cells look compared with healthy breast cells under a microscope. The grade helps your healthcare team understand how quickly the cancer may grow.

A pathologist determines the grade by looking at features of the cancer cells in tissue removed during a breast biopsy or surgery. Breast cancer grades range from 1 to 3:

  • Grade 1. The cancer cells look more like healthy breast cells and tend to grow more slowly.
  • Grade 2. The cancer cells look less like healthy breast cells and tend to grow faster than grade 1 cancer cells.
  • Grade 3. The cancer cells look very different from healthy breast cells and tend to grow more quickly.

Grade is different from stage. Grade describes how the cancer cells look and how quickly the cancer may grow. Stage describes the size of the cancer and whether it has spread. Both can help your healthcare team plan treatment.

Treatment

Treatment for estrogen receptor (ER) positive breast cancer depends on its stage and other features of the cancer cells. Your healthcare team also considers your overall health and whether you have gone through menopause. Hormone therapy is an important part of treatment for most ER positive breast cancers.

For early-stage cancer, treatment often starts with surgery. Other treatments may be recommended to lower the risk of the cancer coming back. If breast cancer has spread to other parts of the body, treatment can help control the cancer, ease symptoms and help you live longer.

Hormone therapy

Hormone therapy for breast cancer blocks the effects of estrogen on breast cancer cells or lowers the amount of estrogen in the body. This can slow the growth of ER positive breast cancer or stop it from growing.

The hormone therapy that's right for you depends on several factors, including whether you've gone through menopause. After menopause, the body continues to make smaller amounts of estrogen in other ways.

Types of hormone therapy include:

  • Selective estrogen receptor modulators. These medicines block estrogen from attaching to estrogen receptors in breast cancer cells. Tamoxifen is one example.
  • Aromatase inhibitors. These medicines lower the amount of estrogen the body makes. Examples include anastrozole, letrozole and exemestane.
  • Selective estrogen receptor degraders. These medicines block estrogen receptors and cause the receptors to break down.
  • Ovarian suppression. For people who haven't gone through menopause, medicines or surgery can stop the ovaries from making estrogen.

Hormone therapy for early-stage ER positive breast cancer often continues for several years. How long you need hormone treatment depends on your risk of the cancer coming back and other factors. Taking hormone therapy for as long as recommended can help lower the risk of the cancer returning.

Side effects of hormone therapy depend on the treatment. They may include hot flashes, joint pain, vaginal dryness and changes in bone health. Some hormone treatments can affect fertility. If side effects make it hard to continue treatment, tell your healthcare team. There may be ways to manage the side effects or change your treatment.

Surgery

Surgery is a common treatment for early-stage ER positive breast cancer. When recommending surgery, your healthcare team considers the size and location of the cancer, your overall health and other factors. You and your healthcare team can talk about the options and decide what's right for you.

Types of breast cancer surgery include:

  • Lumpectomy. During a lumpectomy, the surgeon removes the breast cancer and a small amount of healthy tissue around it. Most of the breast stays in place.
  • Removing the breast with cancer. A mastectomy is surgery to remove breast tissue. There are several types. A total mastectomy, also called a simple mastectomy, removes the breast tissue, skin, nipple and areola. Other types may keep some of the breast skin or the nipple. These include skin-sparing mastectomy and nipple-sparing mastectomy.
  • Checking the first lymph nodes. A sentinel node biopsy is surgery to check whether breast cancer has spread to nearby lymph nodes. The sentinel nodes are the first few lymph nodes where breast cancer is likely to spread. The surgeon removes these nodes and sends them to a lab to check for cancer. If no cancer is found, the surgeon usually doesn't take out more lymph nodes.
  • Removing more lymph nodes. An axillary lymph node dissection is surgery to remove more lymph nodes from the armpit. Your healthcare team may advise it if tests show that cancer has spread to several lymph nodes or if more lymph nodes need to be removed for another reason. Finding cancer in a sentinel lymph node doesn't always mean you need this surgery.
  • Removing the breast without cancer. Some people who have cancer in one breast may choose to have the other breast removed. This surgery is called prophylactic mastectomy. It can lower the risk of getting cancer in the other breast. Your personal risk factors, family history and preferences can help you and your healthcare team decide whether this surgery is right for you.

If you have a mastectomy, you may choose to have breast reconstruction to restore the shape of the breast. Options may include breast reconstruction with implants or reconstruction using your own tissue. You may have reconstruction at the same time as the mastectomy. Or you may have it later. If you're considering reconstruction, ask your healthcare team for a referral to a plastic surgeon before breast cancer surgery.

Radiation therapy

Radiation therapy uses powerful energy to kill cancer cells. Radiation therapy for breast cancer often is recommended after a lumpectomy to kill cancer cells that may remain in the breast. Sometimes, radiation therapy also may be done after a mastectomy.

Radiation therapy also can help ease symptoms if breast cancer has spread to other parts of the body.

Side effects depend on the part of the body being treated. They may include tiredness and skin changes in the treated area.

Targeted therapy

Targeted therapy, sometimes called biological therapy for cancer, uses medicines that attack certain features of cancer cells. Some targeted medicines are used along with hormone therapy to treat ER positive breast cancer.

Medicines called CDK4/6 inhibitors block proteins that cancer cells need to grow and divide. These medicines may be used for some early-stage ER positive, HER2-negative breast cancers that have a higher risk of coming back. CDK4/6 inhibitors also are commonly used to treat ER positive, HER2-negative breast cancer that has spread to other parts of the body.

Other targeted medicines may be options if testing finds certain changes in the cancer cells. These test results can help your healthcare team choose treatments that are more likely to work.

Side effects depend on the medicine. Your healthcare team may use blood tests and other tests to check for side effects during treatment.

Chemotherapy

Chemotherapy for breast cancer uses strong medicines to kill cancer cells. Many people with early-stage ER positive breast cancer don't need chemotherapy.

For some early-stage ER positive breast cancers, genomic tumor testing can help show whether chemotherapy is likely to help. Your healthcare team also considers the stage, tumor grade and other features of the cancer when deciding whether to recommend chemotherapy.

Chemotherapy also may be used if ER positive breast cancer has spread to other parts of the body or stops responding to other treatments.

Side effects depend on the medicines used. They may include tiredness, nausea, hair loss and a higher risk of infection. Some chemotherapy medicines can affect fertility.

Alternative medicine

No alternative medicine treatments have been proved to cure breast cancer. But some complementary approaches may help ease symptoms and side effects of cancer treatment. Other approaches, such as special diets and supplements, may not have proven benefits and could interfere with your treatment.

Complementary medicine for fatigue

Fatigue is common during and after breast cancer treatment. Cancer-related fatigue can make you feel very tired even after you've rested. For some people, it can continue after treatment ends. Complementary treatments may help ease fatigue when used along with medical care.

If fatigue is making everyday activities harder, tell your healthcare team. Your care team can look for possible causes and recommend ways to help. These complementary treatments also may help:

  • Expressing your feelings. Find a way to share or work through your emotions. You might write in a journal, join a support group or talk with a counselor.
  • Try gentle exercise. Ask your healthcare team what kinds of exercise are safe for you. You might try walking, swimming, yoga or tai chi. Start slowly and add more activity as you feel able.
  • Practice mindfulness. Mindfulness helps focus on the present moment. Mindfulness programs may help ease cancer-related fatigue. Ask your healthcare team about programs that may be available to you.

Diets and supplements

You may wonder whether changing your diet or taking supplements can help treat estrogen receptor (ER) positive breast cancer. No specific diet, including a ketogenic diet — also called a keto diet — has been proved to treat or cure breast cancer. Vitamins, herbs and other supplements haven't been proved to treat or cure breast cancer either. Some supplements can interfere with cancer treatments. Talk with your healthcare team before taking vitamins, herbs or other supplements during treatment.

You also may have questions about foods that contain plant estrogens, such as soy and flaxseed. Plant estrogens aren't the same as the estrogen made by the body. Research suggests that eating soy foods is safe for people with ER positive breast cancer and may lower the risk of the cancer coming back. Flaxseed also is likely safe to eat, but more research is needed. Talk with your healthcare team if you have questions about adding flaxseed to your diet.

Coping and support

An estrogen receptor (ER) positive breast cancer diagnosis can bring many emotions. You also may be facing tests, treatments and important decisions about your care. There is no one right way to cope. Give yourself time to find the information and support that are most helpful to you.

Learn about your ER positive breast cancer

Learning about your cancer can help you understand your treatment options and take part in decisions about your care. Ask your healthcare team about the type and stage of your breast cancer and the results of tests for hormone receptors and HER2. You also can ask for trusted sources of information about your diagnosis and treatment.

You don't need to learn everything at once. And not everyone wants the same amount of information. Tell your healthcare team how much you'd like to know and what questions are most important to you.

Talk with others who have had breast cancer

It may help to talk with people who understand what it's like to have breast cancer. Ask your healthcare team about support groups in your community or online. You also can find support through the American Cancer Society. Mayo Clinic Connect is an online community where people share experiences, practical information and support.

Find someone to talk with

Sometimes it can help to talk with someone who has experience supporting people with cancer. Your healthcare team may be able to connect you with a counselor, clergy member or medical social worker.

Let friends and family help

Friends and family may want to help but may not know what you need. Consider telling them about specific ways they can support you. You might ask someone to make a meal, help around your home, drive you to an appointment, care for your pets or listen when you want to talk.

Preparing for an appointment

Make an appointment with a doctor or other healthcare professional if you have any symptoms that worry you or are not going away. If an exam or imaging test shows you might have breast cancer, your healthcare team may refer you to a specialist.

Specialists who care for people with breast cancer include:

  • Breast health specialists.
  • Breast surgeons.
  • Doctors who specialize in diagnostic tests, such as mammograms, called radiologists.
  • Doctors who specialize in treating cancer, called oncologists.
  • Doctors who treat cancer with radiation, called radiation oncologists.
  • Genetic counselors.
  • Plastic surgeons.

What you can do to prepare

  • Write down any symptoms you're experiencing, including any that may not seem related to the reason for which you scheduled the appointment.
  • Write down key personal information, including any major stresses or recent life changes.
  • Write down your family history of cancer. Note any family members who have had cancer. Note how each member is related to you, the type of cancer, the age at diagnosis and whether each person survived.
  • Make a list of all medicines, vitamins or supplements that you're taking and the doses.
  • Keep all records that relate to your cancer diagnosis and treatment. Organize your records in a binder or folder that you can take to your appointments.
  • Consider taking a family member or friend along. Sometimes it can be hard to absorb all the information you get during an appointment. Someone who goes with you may remember something that you missed or forgot.
  • Write down questions to ask your healthcare professional.

Questions to ask your doctor

Your time with your healthcare professional is limited. Prepare a list of questions so that you can make the most of your time together. List your questions from most important to least important in case time runs out. For breast cancer, some basic questions to ask include:

  • What type of ER positive breast cancer do I have?
  • What is the stage of my cancer?
  • Can you explain my pathology report to me? Can I have a copy for my records?
  • Do I need any more tests?
  • What treatment options are available for me?
  • What are the benefits from each treatment you recommend?
  • What are the side effects of each treatment option?

Other questions to ask may include:

  • Will treatment cause menopause?
  • Will treatment affect my being able to become pregnant in the future?
  • How might each treatment affect my daily life? Can I continue working?
  • Is there one treatment you recommend over the others?
  • How do you know that these treatments will benefit me?
  • What would you recommend to a friend or family member in my situation?

More questions to ask:

  • How quickly do I need to make a decision about cancer treatment?
  • What happens if I don't want cancer treatment?
  • What will cancer treatment cost?
  • Does my insurance plan cover the tests and treatment you're recommending?
  • Are there any brochures or other printed material that I can take with me? What websites or books do you recommend?
  • Are there any clinical trials or newer treatments that I should consider?

In addition to the questions that you've prepared, don't hesitate to ask other questions you think of during your appointment.

What to expect from your doctor

Be prepared to answer some questions about your symptoms and your health, such as:

  • When did you first begin having symptoms?
  • Have your symptoms been continuous or occasional?
  • How severe are your symptoms?
  • What, if anything, seems to improve your symptoms?
  • What, if anything, appears to worsen your symptoms?

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