Newly diagnosed breast cancer patients may be surprised to learn that there is not one, but several types of breast cancer. Learning about the different types and subtypes of breast cancer can be very helpful for understanding treatment options, prognosis, and more. Each type of breast cancer behaves and acts differently from the other types, and may require different forms of therapy.

When a tumor is biopsied after removal from the body, a doctor called a pathologist will examine the cells to determine the cancer’s subtype. This information will be included in the pathology report. You can ask your doctor for a copy of this report to keep for your records. One of the more common types of breast cancer you’ll see on a report is ER-positive (ER+).

What Is ER+ Cancer?

ER+ breast cancer simply means that a woman’s tumor cells have receptors that tell cancer to grow in response to estrogen. Estrogen is a hormone produced naturally in the body. An important strategy to prevent ER+ cancer from returning is to block estrogen from reaching those cells.

According to the American Cancer Society, two out of every three breast cancers are hormone dependent. Most ER+ cancers are also PR+, meaning they also grow in response to the hormone progesterone. But this isn’t always the case.

Studies have shown that ER+ breast cancer has the best prognosis of all the breast cancer subtypes, and often responds well to treatment. However, all breast cancers have the potential to return after treatment is completed. For this reason, women with ER+ cancers are typically given a medication to prevent cancer relapse.

Treatment for ER+ Cancer

Treatment will start out in much the same way as it does for women with other types of breast cancer. Surgery — either a lumpectomy or a mastectomy — will be performed to remove the tumor. If necessary, chemotherapy and possibly radiation will be given afterwards.

Once the tumor is removed and all other treatments are completed, you’ll be prescribed an anti-hormonal drug to prevent the cancer’s return. These drugs are usually taken orally at home. It’s recommended that these drugs be taken for five years. However, a study published in The Lancet suggests that these drugs should be given for 10 years to further reduce the chances of recurrence. 

Types of Drugs

There are two classes of these anti-estrogen drugs. Each works to prevent cancer in a different way: One blocks the estrogen from stimulating the estrogen receptors on breast cancer cells, and the other stops the body from producing estrogen altogether.


Tamoxifen is given to premenopausal women to block estrogen receptors on breast cancer cells. Although not without side effects, this class of drug is relatively safe and has been in use for more than 30 years. The most common side effects are mood swings, bone aches, vaginal dryness, and hot flashes. It can also cause thickening of the uterus and, in rare cases, uterine cancer and blood clots. Follow up with your doctor when on these drugs, and report any unusual symptoms.

Aromatase Inhibitors

Another class of these drugs is aromatase inhibitors, which are given to postmenopausal women. These are the drugs that stop estrogen production entirely. The most common of these are letrozole (Femara), anastrozole (Arimidex), and exemestane (Aromasin). These drugs can also cause bone and joint pain, but not clots or uterine thickening.

Ovarian Oblation

Another option for ER+ breast cancer treatment is ovarian ablation. This can be done with drugs, such as leuprorelin (Lupron), with radiotherapy, or with an actual surgical procedure. The surgery, called an oophorectomy, is the removal of the ovaries. An oophorectomy is a serious surgery that can have a profound and permanent effect on a woman’s life, so it should be considered carefully.

Ovarian ablation is most often used for treating women with metastatic cancer and patients who have the BRCA gene. This procedure is still being studied as treatment for early stage cancer.

Estrogen Blockers and Metastatic Cancer

Estrogen blockers can also be very effective at controlling ER+ metastatic cancer. Some people believe that these are not the “big guns” in medical treatment, but they may be just as effective as other forms of chemotherapy at blocking cancer cells. These blockers may also have fewer side effects than other forms of chemotherapy, and can be a very viable option when dealing with a relapse and/or metastasis.

Understanding your options is an important part of making treatment decisions. ER+ cancers are one of the few cancers that have tried and tested preventive drugs that can reduce the risk of relapse.