Risk Management & Treatment

Breast cancer subtypes

Breasts are made up of two main types of cells; the breast lobules, which make milk, and the breast ducts which carry the milk to the nipple. The most common type of breast cancer - known as "ductal carcinoma" starts in the ducts. Less common is "lobular carcinoma," which starts in the breast lobules. 

There are other, very rare types of breast cancer. Inflammatory breast cancer is a very fast growing type of ductal carcinoma. Paget's disease of the breast is a type of ductal carcinoma that affects the nipple and areola. Phyllodes tumors start in the connective tissue of the breast. 


Stages of breast cancer

The  of a cancer refers to whether the cancer has spread beyond the breast, and if so, where in the body the cancer has spread. Measuring the of breast cancer helps doctors decide how to treat it. Breast cancer most often starts as a lump within the breast that can grow and spread: 

  • within the breast
  • to nearby tissue (such as , skin or the chest wall)
  • through the blood stream or lymph system to distant organs (

In breast cancer, there are five major stages.  

  •  0: A  0 breast cancer is known as a ductal carcinoma in situ (), a non-invasive form of the disease. The tumor cells are contained within the ducts of the breasts, and have not invaded beyond the duct. Cancers caught and treated at  0 are very unlikely to recur or spread.
  • 1: A small tumor (< 2 cm) that is contained within the breast and has not spread to the .
  • 2: A  2 breast cancer can be either a larger tumor that involves the breast only, or a tumor that has spread to some  in the armpit.
  • 3: A  3 breast cancer can be either a tumor in the breast that invades the skin or chest muscle, or a tumor that involve several  surrounding the breast (in the armpit, near the collarbone, near the breast bone).  3 breast cancers are sometimes called “locally advanced.”
  • 4 or metastatic: A  4 breast cancer is one that has spread beyond the breast and the regional to another place in the body, such as the bone, lung, and/or liver.   IV breast cancers are also called “advanced” or “.”

Generally, breast cancers diagnosed at stages 1-3 are considered curable, so treatment plans are made with the goal of cure.  breast cancer is often treatable at diagnosis. Over time, breast cancer is likely to progress or recur; sometimes after several different types of treatment. There are many different treatments available for breast cancer, and clinical trials testing new treatments are often available. 

Subtypes and biomarkers 

After a biopsy or surgery confirms breast cancer, pathologists look closely at the cells for additional clues on how to best treat the cancer. All breast cancers are tested for common changes, called tumor biomarkers: estrogen receptor (ER), progesterone receptor (PR), and . The results of these tumor tests play a major role in choice of cancer treatment:

  • ER-positive and PR-positive breast cancers: Breast cancers with these biomarkers are often called "hormone sensitive" breast cancers. These are usually treated with hormone therapy. Chemotherapy may also be recommended depending on the  of the tumor and other factors. A  known as a CDK4/6 inhibitor (Ibrance) has been  approved for treating  or advanced hormone receptor positive,  breast cancer in combination with an aromatase inhibitor. 
  •  breast cancers: these cancers benefit from therapies that target the  molecule. Therapies include  Herceptin (trastuzumab) and Perjeta (pertuzumab). Anti-HER2 therapy is given with chemotherapy in patients with , curable tumors. Patients whose tumors are  and ER-positive receive hormone therapy, as well as chemotherapy and anti-HER2 therapy.
  • ER-negative and PR-negative breast cancers: these are almost always are treated with chemotherapy because hormone therapy does not benefit patients with these types of tumors.
  • Triple-negative breast cancers: tumors that are negative for all three markers are referred to as  or sometimes "" for short. Like other ER-negative breast cancers, triple-negative breast cancers are almost always treated with chemotherapy. People with  mutations are more likely to develop  than any other type of breast cancer. 

Additional tests can be performed on tumor samples to help guide treatment. Prognostic genomic tests can also help guide treatment decisions. For some patients with advanced cancers, tumor testing can look for additional tumor markers to help guide the choice of targeted therapies. At the moment, this type of tumor testing for  is mostly experimental and used within research studies.

Some types of breast cancer are more common in people with inherited mutations linked to cancer. 

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The following organizations offer peer support services for people with, or at high risk for breast cancer:

updated: 02/25/2022

Last updated January 25, 2022