HR+/HER2- breast cancer—or hormone receptor-positive, HER2-negative breast cancer—is the most common subtype of breast cancer. It makes up about 70% of all breast cancer cases. 

HR+/HER2- breast cancer involves tumor cells that test positive for hormone receptors and negative for HER2 proteins. Cancer cells with estrogen or progesterone hormone receptors can grow in response to those hormones.

When tumors are human epidermal growth factor receptor 2-negative (HER2-), they contain few to no HER2 proteins. These proteins cause cancer cells to grow quickly.

Symptoms of HR+/HER2- breast cancer can vary but often include a breast lump, pain, and fatigue. Once detected, several treatment options are available.

The symptoms of HR+/HER2- breast cancer are similar to those of other breast cancers and may vary depending on how advanced the cancer is. Common symptoms include:

• A lump in the breast or armpit
• Breast pain
• Fatigue
• Thickening of the skin on the breast or armpit 
• A change in the size or shape of the breast
• Skin dimpling or puckering 
• Inverted nipple
• Nipple discharge (other than breast milk)
• Redness and swelling around the nipple

HR+/HER2- breast cancer occurs when cells in the breast tissue mutate and grow uncontrollably. Researchers aren’t certain what causes breast cancer but have determined several risk factors. In addition to genetic mutations, hormonal changes likely increase the risk of developing HR+/HER2- breast cancer.

Risk Factors

Several factors may increase the risk for HR+/HER2- breast cancer, including:

• Female sex
• Older age
• History of breast cancer
• History of noncancerous breast conditions
• Dense breast tissue
• History of radiation to the chest area 
• Obesity 
• Excessive alcohol use 
• Inactive lifestyle

Being exposed to more estrogen over your lifetime may also increase your risk. You may have been exposed to more estrogen if you:

• Started menstruating before age 12
• Started menopause at a later age 
• Used hormone replacement therapy (HRT)
• Didn’t have children
• Didn’t breastfeed children 
• Used oral birth control pills

If a healthcare provider suspects you may have cancer, they will refer you to an oncologist, a medical doctor specializing in diagnosing and treating cancer. In addition to taking your medical history and performing a physical exam, your oncologist may run these diagnostic tests:

• Mammogram: A mammogram takes X-ray images of your breasts from different angles and can detect any tumors.
• Other imaging tests: Your healthcare team may also recommend other imaging studies, including an ultrasound or magnetic resonance imaging (MRI).
• Breast biopsy: Your provider may take a tissue sample to examine the cells under a microscope. 
• Blood tests: Your healthcare team can test your electrolytes, fats, proteins, glucose, and enzymes for signs of cancer.
• Genetic testing: This can help identify if you have a gene mutation that has increased your risk of cancer.
• Immunohistochemistry (IHC) test: This test can determine whether HER2 proteins are present in any cancer cells.
• Hormone receptor test: This can determine whether any cancer cells have receptors for estrogen or progesterone.

Breast Cancer Staging

After diagnosis, your healthcare team will determine the cancer’s stage. Cancer staging is a process to determine how advanced cancer is and how far it has spread throughout your body. 

In addition to determining the hormone receptor and HER2 protein status, healthcare teams use the TNM system to identify the stages. This system notes:

• (T): Tumor size
• (N): Nearby lymph node involvement
• (M): Metastasis (spread) to different areas of the body
• Grade: A measurement of how much the cancer cells look like normal cells 
• Hormone receptor status: Whether the cancer has estrogen or progesterone receptor proteins
• HER2 status: How much HER2 protein the cancer makes

Your oncologist will use scoring of these different aspects to determine your cancer stage, which may be stages 0-4.

Your treatment plan will depend on several factors, including your cancer stage, age, menopause status, and overall health. 

For most people with HR+/HER2- breast cancer, hormone therapy is the go-to treatment because it targets the hormone receptors in the cancer cells. Hormonal cancer treatments are different from hormone replacement therapy. Hormonal cancer treatments may include:

• Selective estrogen receptor modulators (SERMs): These attach to estrogen receptors, preventing estrogen from attaching to the receptors.
• Aromatase inhibitors: These block your body’s estrogen production by blocking aromatase, an enzyme that helps make estrogen.
• Luteinizing hormone-releasing hormones (LHRHs): These agents prevent your ovaries from producing estrogen.
• Ovary removal (oophorectomy): Surgical removal of your ovaries will prevent you from producing estrogen.

Your healthcare team may recommend hormone therapy alone or with other cancer treatments. For example, hormone therapy may be used to shrink a tumor size before surgery. It can also be used with chemotherapy. 

It may not be possible to prevent breast cancer, but you can take steps to help lower your risk. These include:

• Maintain a healthy weight
• Be physically active every day
• Avoid or limit alcohol use
• Avoid or quit smoking
• Talk with your healthcare provider about the risks of hormone replacement therapy before starting it
• Eat a nutritious diet rich in vegetables and fruits and low in red or processed meats

If your healthcare team has determined that you’re at high risk for developing breast cancer, some treatments may reduce your risk. Your healthcare team may recommend:

• Medications: Nolvadex (tamoxifen) and Evista (raloxifene) block the effects of estrogen on breast tissue, which may reduce the risk of hormone receptor-positive breast cancer. Aromatase inhibitor medications may reduce the risk of breast cancer in people who have gone through menopause. 
• Surgery: People who are at very high risk for breast cancer may choose to have a prophylactic mastectomy (having their breasts removed ). 
• Observation: People at high risk for breast cancer may want to see their healthcare provider every 6-12 months for breast exams, mammograms, and other tests.

HR+/HER2- breast cancer and its treatments may lead to serious complications. During and after treatment, your healthcare team will monitor you closely for potential complications and related conditions, such as:

• Endometrial cancer: People who receive the drug Nolvadex (tamoxifen) for breast cancer have a higher rate of developing endometrial cancer. 
• Other cancers: People who have had breast cancer before are at an increased risk of developing another type of breast cancer. They may also develop cancer of the uterus, ovaries, thyroid, stomach, colon, esophagus, salivary glands, and skin. 
• Osteoporosis: Treatment with aromatase inhibitors may cause low bone density and raise the risk of osteoporosis. 

Having cancer and going through its treatment may affect you mentally and emotionally. Many people also report concerns about intimacy and relationships after breast cancer treatment. Consider talking with a therapist or support group who can help you.

Some people aren’t able to achieve remission (a period where healthcare providers can’t find cancer cells anymore and symptoms go away) but can live with breast cancer. Others achieve remission but need to be monitored for cancer coming back.

Your healthcare team will likely perform follow-up physical exams, blood tests, and imaging studies. They will also likely ask about any new symptoms or treatment side effects.