BREAST CANCER ANATOMY AND HOW CANCER STARTS
The breast is a highly complex part of the human body. It goes through many changes over a lifetime – from birth, puberty, pregnancy and breastfeeding, right through to menopause.
Breast tissue extends from the collarbone, to lower ribs, sternum (breastbone) and armpit. Each breast contains 15-20 sections called lobes and each lobe has many smaller sacs, or lobules (glands). It is these lobules that produce milk in breastfeeding women. The lobes and lobules are connected to the nipple by tubes called ducts, which carry milk to the nipple. The nipple is located at the centre of the areola, the dark area of skin surrounding the nipple.
The breast and armpit contain lymph nodes that belong to the lymphatic system- a network of nodes and tubes that drain fluid (lymph) and transport white blood cells (immune cells involved in fighting against infections). The remainder of the breast consists of fatty and connective (or fibrous) tissue.
HOW DOES CANCER START IN THE BREAST?
Healthy cells are the basic building blocks of all tissues in the body. Normal cells are programmed to grow and divide in an orderly and controlled manner. However, sometimes, cells become damaged. They may develop (or have inherited) abnormalities (also called ‘mutations’) in their genes, which are the cell’s instructions for how to behave. Accumulating these abnormalities can lead to abnormal cell growth.
Breast cancer occurs when the cells in the breast divide and grow out of control. Cancerous cells can invade and damage the surrounding tissues. If they continue to grow and spread, they could become life-threatening.
Breast cancer usually begins in the ducts that carry milk to the nipple (called ductal carcinoma), or within the lobules (called lobular carcinoma). In rare cases, other cancer types can also occur in the breast, such as lymphomas (cancer of the lymphatic system) or sarcomas (cancer of the soft tissues).
Although a lump in the breast is a common symptom of breast cancer, not all breast cancers have obvious symptoms. For example, some lumps may be too small to be felt, but can be detected with a screening mammogram or other tests. There are also some benign (non-cancerous) conditions that can cause lumps in the breast, such as cysts. If you notice any new lumps or other unusual breast changes, please consult with your doctor.
HOW DOES CANCER SPREAD BEYOND THE BREAST?
Breast cancer can spread through nearby tissue, or through the body via the lymphatic system and blood.
- Tissue: the cancer spreads from the original site and grows into nearby areas (often referred to as “invasive”).
- Lymphatic system: breast cancer cells can enter nearby lymph tubes (vessels), grow in nearby lymph nodes or travel through lymph vessels to other parts of the body.
- Blood: breast cancer cells can enter and travel through nearby blood vessels to other parts of the body.
Usually, a surgical procedure to remove one or more nearby lymph nodes is needed to determine how far cancer has spread. When cancer cells are found in one or more lymph nodes