What is breast cancer?

Cancer is the name for a group of diseases that develop when the body’s cells grow in an uncontrolled way and spread into the body’s tissues. Breast cancer is cancer that starts in the breast tissue

What does a breast look like on the inside?

Breasts are made up of lobules and ducts surrounded by fatty and connective tissue:

  • lobules produce breast milk
  • ducts carry milk to the nipple.
Illustration of a woman's breast including showing ductal carcinoma in situ & invasive breast cancer
Illustration of a woman's breast including showing ductal carcinoma in situ & invasive breast cancer

Close to the breasts are a number of lymph nodes. These are part of the lymphatic system and help to protect the body from infection. The closest lymph nodes to the breast are in the armpit (axillary nodes). There are also lymph nodes under the breastbone (internal mammary nodes) and in the neck (supraclavicular nodes).

How does breast cancer develop?

Breast cancer can start in the ducts or lobules of the breast. Sometimes cancer cells stay in the ducts and lobules of the breast. This is called non-invasive breast cancer. If the cancer cells spread into the surrounding tissue, this is called invasive breast cancer. The site where the cancer starts is called the primary cancer.

Sometimes, breast cancer cells travel in the bloodstream or lymphatic system to other parts of the body such as the bones or liver. This is called metastatic breast cancer (or secondary or advanced breast cancer).

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