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What Is Breast Cancer?

Having breast cancer means that some cells in your breast are growing abnormally. Learning about the different types and stages of breast cancer can help you take an active role in your treatment.

Changes in Your Breast

Your entire body is made of living tissue. This tissue is made up of tiny cells. You can’t see these cells with the naked eye. Normal cells reproduce (divide) in a controlled way. When you have cancer, some cells become abnormal. These cells may divide quickly and spread into other parts of the body.

Cutaway view of normal breast

Normal breast tissue is made of healthy cells. They reproduce new cells that look the same.

Cutaway view of breast with tumor

Noninvasive breast cancer (carcinoma in situ) occurs when cancer cells are only in the ducts.

Cutaway view of breast with tumor

Invasive breast cancer occurs when abnormal cells move out of the ducts or lobules into the surrounding breast tissue.

Cutaway view of breast with tumor

Metastasis occurs when cancer cells move into the lymph nodes or bloodstream and travel to another part of the body.

 

Stages of Breast Cancer

Several tests are used to measure the size of a tumor and learn how far it has spread. This is called staging. The stage of your cancer will help determine your treatment. Based on National Cancer Institute guidelines, the stages of breast cancer are:

  • Stage 0. The cancer is noninvasive. Cancer cells are found only in the ducts (ductal carcinoma in situ).

  • Stage I. The tumor is 2 cm or less in diameter. It has invaded the surrounding breast tissue, but has not spread to the underarm lymph nodes.

  • Stage II. The tumor is larger than 2 cm or has spread to the lymph nodes under the arm.

  • Stage III. The tumor is larger than 5 cm. Or the tumor has spread to the skin, chest wall, or nearby lymph nodes.

  • Stage IV. The tumor has spread to the bones, lungs, or lymph nodes far away from the breast.

Recurrent breast cancer. When the cancer returns despite treatment.

 

Online Medical Reviewer: MMI board-certified, academically affiliated clinician
Online Medical Reviewer: Moloney Johns, Amanda, PA-C, MPAS, BBA
Last Review Date: 9/28/2013
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