What is breast cancer

The breast is a gland that consists of breast tissue supported by connective tissue (flesh) surrounded by fat. The easiest way to understand how the inside of the breast is formed is by comparing it to an upturned bush. Its leaves are known as lobules and they produce milk that drains into ducts that are the branches of the breast tree. These in turn drain into 12 or 15 major or large ducts which empty onto the surface of the nipple, just like the branches of a tree drain to the trunk. Breast cancer develops from the cells that line the breast, lobules and the draining ducts. Cancer cells that remain confined to the lobule and the ducts are called 'in situ' or 'non-invasive'. They are sometimes also referred to as pre-cancers in recognition of the fact that these cells have not yet gained the ability to spread to other parts of the body, which is the feature that most people associate with cancer. An invasive cancer is one where the cells have moved outside the ducts and lobules into the surrounding breast tissue.