What Is Triple-Positive Breast Cancer?
Triple-positive breast cancer is cancer whose growth is fueled by the hormones estrogen and progesterone and the HER2 protein.
A breast cancer is triple-positive when it has:
receptors for estrogen (estrogen receptor-positive)
receptors for progesterone (progesterone receptor-positive)
high levels of HER2 proteins that act as receptors (HER2-positive)
When the hormones bind to their receptors, they tell the cell to grow. And too many HER2 proteins make breast cells grow and divide in an uncontrolled way.
There are many medicines available to treat triple-positive breast cancer. If you’re one of the 10% of people diagnosed with this type of breast cancer, your doctor will likely recommend hormonal therapy, chemotherapy, and targeted therapy as part of your treatment plan.
Signs and symptoms of triple-positive breast cancer
The symptoms of triple-positive breast cancer are the same as most other types of invasive breast cancer. The most common symptom is a lump or mass in the breast or underarm.
Diagnosis of triple-positive breast cancer
Like other types of breast cancer, mammograms or breast MRI are often the first step in identifying an abnormal area. If the imaging test results suggest breast cancer, your doctor will likely recommend a biopsy. Testing the tissue that’s removed determines if the cancer cells have estrogen and progesterone receptors and the amount of HER2 proteins.
To determine the best treatment for triple-positive breast cancer, doctors consider the size and grade of the tumor, as well as whether cancer cells are found in the lymph nodes (lymph node status). All this information is used to identify the stage of the cancer.
The stage of an invasive breast cancer is commonly written as a Roman number of I, II, III, or IV. Stage IV breast cancer — also called metastatic breast cancer — is cancer that has spread to parts of the body away from the breast, such as the liver or bones.
Treatments for triple-positive breast cancer
Depending on the stage of the cancer, treatments for triple-positive breast cancer may include:
Surgery: Mastectomy or lumpectomy are the two main surgical options.
Radiation therapy: If you decided to have lumpectomy, your doctor will usually recommend radiation therapy after surgery. Depending on the size and lymph node status of the cancer, radiation therapy also may be recommended after mastectomy. If you’ve been diagnosed with metastatic triple-positive breast cancer, radiation may be recommended to ease pain or control the cancer in a specific area.
Chemotherapy: Chemotherapy can be used to shrink the size of the cancer before surgery.
Targeted therapy: Because triple-positive breast cancer has too many HER2 receptors, it’s likely to respond to anti-HER2 medicines that target the HER2 protein, including Herceptin (chemical name: trastuzumab) and Perjeta (chemical name: pertuzumab). Targeted therapy is often combined with chemotherapy. Targeted therapy along with chemotherapy is recommended for some stage I and for most stage II and stage III triple-positive breast cancers.
Hormonal therapy: Because triple-positive breast cancer has receptors for both estrogen and progesterone, hormonal therapy medicines, such as tamoxifen and the aromatase inhibitors, tend to work well, and are prescribed for all triple-positive breast cancers, regardless of stage.
— Last updated on August 14, 2025 at 5:51 PM