What is cancer?

Our bodies are made up of trillions of cells, the building blocks of all life. Cells are organized into tissues and organs. Normal cells in your body are constantly growing, dividing and dying in a controlled manner. Sometimes cells can become abnormal. Cancer occurs when abnormal cells begin to divide and grow uncontrollably and have the ability to spread to the surrounding tissue.

What is breast cancer?

Cancer that starts in the breast is called breast cancer. Our breasts are made up of lobules (milk-producing glands), ducts (tubes that carry milk from the lobules to the nipple) and other types of tissue.

Breast cancer most commonly develops in the cells lining the milk ducts and less commonly in the lobules. Cancerous cells can remain in the ducts or lobules (this is referred to as “in situ” cancer) or they can break through into surrounding breast tissue (this is invasive or infiltrating cancer).

What causes breast cancer?

No one knows exactly what causes breast cancer.  There is no single cause of cancer, but rather multiple factors, known and unknown, contribute to the disease. Many women will have some of the known risk factors that can increase the chance of developing breast cancer, but having one or more risk factors does not automatically mean you will be diagnosed. However, many women who do get breast cancer do not have any known risk factors, other than being a woman and growing older.

What are the symptoms of breast cancer?

You may have no symptoms in the early stages of breast cancer. You may have gone for a screening mammogram and an abnormality was found, or you may have noticed a change in your breast. Breast cancer is usually first noticed as a lump in the breast. Other signs might include:

  • A lump or swelling in the armpit
  • Thickening in the breast
  • Changes in the size or shape of one breast compared with the other
  • Dimpling, puckering or in-drawing of the skin
  • Redness, swelling and increased warmth in the affected breast
  • Skin that is pitted (like an orange peel)
  • A nipple that turns inwards (and wasn’t like that before)
  • Crusting or scaling on the nipple
  • Discharge or bleeding from the nipple

Links to more information

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What is Breast Cancer?
Canadian Cancer Society

About Breast Cancer
Canadian Breast Cancer Foundation

Understanding Breast Cancer
Breastcancer.org

What is Breast Cancer?
American Cancer Society