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What is breast cancer?

Having breast cancer means that some cells in your breast have changed and are growing out of control. 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 which is made up of tiny cells. You cannot see these cells with the naked eye. Normal cells reproduce in a controlled way and grow when your body needs them; they die when your body does not need them any longer. When you have cancer, some cells become abnormal, dividing quickly, not dying when they should and spreading into other parts of the body.

Usually, breast cancer can either begin in the cells of the lobules, the milk-producing glands, or the ducts, the passages that drain milk from the lobules to the nipple. Less commonly, breast cancer can begin in the stromal tissues which include the fatty and fibrous connective tissues of the breast. 

Over time, cancer cells can invade nearby healthy breast tissue and make their way into the underarm lymph nodes, small organs that filter out foreign substances in the body. If cancer cells get into the lymph nodes, they can have a pathway to other parts of the body. The breast cancer’s stage refers to how far the cancer cells have spread beyond the original tumor.

 


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, and cancer cells are found only in the ducts.
  • Stage I: The tumor is 2 cm (about ¾ of an inch) or less in diameter and has invaded the surrounding breast tissue. Tiny amounts of cancer cells may be found in the underarm lymph nodes.
  • Stage II: The tumor is larger than 2 cm and has not spread nodes, or the cancer is less than 5 cm across and has spread to the lymph nodes under the arm.
  • Stage III: The tumor is less than 5 cm (2 inches) across, and there is a lot of cancer in your underarm lymph nodes, or it has spread to other lymph nodes. Or the tumor is larger than 5 cm and has spread to lymph nodes. Or the tumor is any size and has spread to the skin, chest wall, and maybe to nearby lymph nodes.
  • Stage IV: The tumor has spread beyond the breast to the bones, lungs, liver, brain or lymph nodes far away from the breast.