Triple-Positive Breast Cancer

April 10, 2025

This page was reviewed under our medical and editorial policy by Nikhila Kethireddy, M.D., assistant clinical professor, and Susan Yost, Ph.D., staff scientist, Department of Medical Oncology & Therapeutics Research, City of Hope^® Cancer Center Duarte

One of the first steps after a breast cancer diagnosis is determining the subtype of breast cancer. This helps guide treatment. Triple-positive breast cancer is one of the four subtypes. Fewer than 10% of breast cancers in women are triple-positive, making this the third most common form of breast cancer.

What Is Triple-Positive Breast Cancer?

Triple-positive breast cancer has three known receptors in or on the surface of its cells. Receptors are molecules, and when they bind to certain substances in the blood, it triggers a signal, or reaction, in the cells.

Two of the receptors are female hormone receptors for estrogen and progesterone, making the cells:

ER-positive (ER+) — estrogen receptors

PR-positive (PR+) — progesterone receptors

This subtype of breast cancer also carries receptors for the human epidermal growth factor receptor 2 (HER2) protein. This protein is involved in the normal growth of cells. Therefore, this type of breast cancer is also HER2-positive (HER2+).

If a cancer is found to have both hormone receptors (ER+ and PR+) and has more HER2 proteins than normal (HER2+), it is labeled as triple-positive breast cancer.

Is It an Aggressive Form?

Because triple-positive breast cancers are always HER2-positive, they are considered aggressive. The HER2 protein helps the cancer cells grow quickly. However, medications have been developed that specifically target this protein.

HER2-positive cancers may spread to other parts of the body (metastasize), such as the brain. HER2-positive breast cancer is also more likely to return after treatment compared to other non-HER2 breast cancers. This is called breast cancer recurrence.

Triple-Positive Breast Cancer Symptoms

The symptoms of triple-positive breast cancer are the same as those for other forms of breast cancer, and they may include:

• Lump near or in the breast or armpit (axilla)
• Breast pain
• Discharge or blood from the nipple
• Swelling or a feeling of thickness in the breast
• A change in breast shape or size
• Dimpling or puckering of the breast skin
• Scaling or redness of the skin (breast cancer rash)
• Inverted nipple

What Causes Triple-Positive Breast Cancer?

No single cause triggers triple-positive breast cancer. Researchers suspect genetic mutations activate excessive growth of cancer cells, and they continue to investigate the causes of these mutations. There are known risk factors for the development of breast cancer. A significant risk is older age. Other risk factors may include:

• Beginning menstruation at a young age
• Never giving birth or having first birth at an older age
• Starting menopause later than average
• Taking hormones such as estrogen and progestin
• Having dense breast tissue
• A personal history of a noncancerous (benign) breast disease
• Having a first-degree relative (mother, sister, daughter) with a history of breast cancer
• Inherited changes in the BRCA1 or BRCA2 genes or other genes that increase cancer risk
• Obesity
• Alcohol use
• Treatment with radiation therapy to the chest/breast

Triple-Positive Breast Cancer Treatment

Breast cancer treatment typically involves a combination of therapeutic options, including surgery, radiation therapy, chemotherapy and hormone therapy. Medications that directly target the two hormone receptors and the HER2 protein play a significant role in treating triple-positive breast cancer.

In addition to triple-positive status, other factors considered when determining therapy include:

• Whether or not the patient has gone through menopause
• Stage (extent) of the cancer
• Tumor grade (abnormality and growth rate of cancer cells)

Treatment options for triple-positive breast cancer may include the following.

Systemic therapy

Hormone therapy for breast cancer: This treatment targets hormone receptor-positive (HR+) cancers by slowing or stopping the growth of the tumor cells. Hormone therapy works by interfering with the body’s ability to produce the hormones estrogen and progesterone or by disrupting their effects on tumor cells, lowering the chance of the cancer coming back after surgery.

Breast cancer chemotherapy: Chemotherapy in combination with HER2 targeted treatment may be given before surgery to reduce the size of the tumor and decrease the amount of tissue to be removed during the surgery. This is known as neoadjuvant therapy. The patient may also receive chemotherapy after surgery to destroy any remaining cancer cells. Treatment after surgery is called adjuvant therapy.

Breast cancer targeted therapy: This treatment attacks specific cancer cells to keep them from growing and spreading. With triple-positive breast cancer, the HER2 proteins are targeted. This is a type of adjuvant therapy when used with other anticancer drugs.

Surgery

A majority of patients with breast cancer will have surgery to remove the tumor. The types of breast cancer surgeries include the following.

Lumpectomy: This breast-conserving surgery (BCS) removes the cancer and some surrounding tissue, but not the whole breast. Lymph node sampling called sentinel lymph node biopsy is generally done. If the cancer is near the chest wall, part of it may also be removed.

Total mastectomy: This procedure removes the entire breast. Lymph nodes in the armpit may be removed as well to check for cancer spread.

Modified radical mastectomy: The whole breast is removed along with lymph nodes from the armpit. The surgery may also remove the nipple and skin covering the breast.

Surgery to rebuild or reconstruct the breast, should the patient desire it, may be done at the time of a mastectomy or later. The patient will generally be referred to a plastic surgeon before surgery to discuss available options.

Radiation therapy

Radiation therapy for breast cancer is a treatment using high-energy X-rays or other forms of radiation. This therapy destroys any remaining cancer cells and helps keep the cancer from growing.

External radiation therapy: A machine outside the body targets only the area of cancer with radiation.

Internal radiation therapy: Radioactive substances are placed directly into or near the cancer. The substances may be in the form of seeds, wires or catheters.

Triple-Positive Breast Cancer Survival Rate

Survival rates are based on the percentage of people who were still alive after a cancer diagnosis or start of treatment. Most commonly, a five-year duration is used to measure the survival rate.

Survival statistics for triple-positive breast cancer are challenging to find. The overall five-year survival rate reported in a 2023 study in Frontiers in Oncology including 60 patients with triple-positive breast cancer was 96.7%