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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, changing shape. These cells may divide quickly and spread into other parts of the body.

Cross section of breast.

Cross section of breast showing noninvasive breast cancer.

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

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

Cross section of breast showing invasive breast cancer.

Outline of woman from head to mid-thigh.  Arrows show breast cancer spreading to multiple organs.

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

Metastasis happens 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 American Cancer Society 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.

Note: Your healthcare provider may use the TNM (tumor node metastases) method for staging. You will be given more information about this if needed.

Recurrent breast cancer is when the cancer returns despite treatment.

Author: StayWell Custom Communications
Last Annual Review Date: 6/1/2017
Copyright © The StayWell Company, LLC. except where otherwise noted.
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