How common is breast cancer?
Breast cancer is the most common type of cancer among women. Each year there are approximately 41,000 new cases in the UK and over one million worldwide. Although breast cancer is much more common in women, it can also affect men and in the UK approximately 300 men every year develop breast cancer. One in nine women will develop breast cancer at some time in her life.
This booklet covers possible causes, screening and symptoms of breast cancer, and how it is diagnosed and treated. It also contains important information to help women cope with the disease.
Much research continues into the causes of breast cancer, as well as new ways to prevent, diagnose and treat it. As a result men and women diagnosed now with breast cancer have a much higher chance of living and surviving it.
How do breasts grow and change?
Breasts start to develop a few weeks after the embryo is formed in the womb. At about six months of pregnancy, some cells grow inwards and these cells develop to form what will be the baby’s nipples and milk ducts. By the time the baby is born the basic breast structure is in place.
In most girls, breasts start to develop between the ages of nine and eleven years but this process can begin earlier or later. Even when fully developed, the breasts at this stage are not capable of producing milk.
It is also common for boys to get some breast development during puberty. This can be embarrassing but is usually only temporary and in over 80 per cent disappears within a year or two.
During pregnancy a woman’s breasts increase in size and approximately double in weight as milk-producing cells multiply and the system of ducts expands. The nipples get darker in colour during pregnancy and the blood vessels under the skin of the breast become more prominent. All these changes take place as a result of the various hormones that are produced during pregnancy and most of these changes are only temporary.
What is a breast made of?
The easiest way to understand how the inside of the breast is arranged is by comparing it with an upturned tree. The leaves of the breast ‘tree’ are known as lobules. They produce milk, which drains along the branches of the breast tree forming a network of small ducts. These in turn drain into 12 or 15 large ducts, which empty on to the surface of the nipple. The nipple is equivalent to the bush’s trunk.
As with a tree, the breast’s branching network of ducts is irregular and complicated and not arranged symmetrically into segments as, for example, is found in an orange.
The breast also contains blood and lymph vessels. The lymph vessels carry clear fluid called lymph from the breast tissue to lymph nodes close to the breast. The nodes that drain most of the lymph from the breast are in the area under the arm and are called the axillary nodes. A small amount of lymph does drain inward to lymph nodes underneath the breastbone.
Lymph nodes are important in the body’s defence systems, and are involved with dealing with bacteria, cancer cells or other harmful substances. Cancer cells that enter lymph channels can pass to draining lymph nodes where some of the cells grow and result in lymph node enlargement.
The space between the branches of the breast tree is made up of fat and this gives the breast a soft feel. Women’s breasts are rarely the same size as each other and breasts can feel different at different times of the monthly menstrual cycle, often swelling and becoming tender in the week before a period. As a woman gets older the amount of breast tissue in the breast reduces and is replaced by fat so the breasts become softer.
What is breast cancer?
Many cells in the human body are growing at any one time but their growth is very carefully controlled so that the number of cells produced matches the number of cells that are dying. A cancer develops when cells grow or divide at a faster rate than normal but escape from the normal mechanisms that control cell growth.
This results in the development of a cancerous lump (primary tumour), which if untreated gets bigger and bigger, as the cells continue to divide and so multiply. Lumps are common in the breast and there are many causes for breast lumps other than breast cancer. Only about one in eight lumps is cancer (malignant growth) and the rest are not serious or life threatening and do not spread to other areas of the body. These are known as benign lumps. The most common treatment for a cancer in the breast is surgery to remove the cancer.
If the lump continues to grow, some of the cells may develop the ability to move away from the lump to other parts of the body, where they grow to form secondary tumours. This is called spread or metastasis of a cancer.
The cancer cells can spread if they enter the lymph channels, through which they travel to other lymph nodes where they can continue to grow and result in enlarged lymph glands which may be felt, for instance, as a lump under the arm.
If cancer is present in the lymph nodes this can be treated by surgery to remove the affected nodes or by radiotherapy, which is effective at destroying cancer cells.
Cells can also get into blood vessels and cells that get into the bloodstream can result in the development of new lumps (metastases) in different areas of the body.
If cancer cells start to grow in an important area such as the lungs, liver or brain, or if cells grow in bones, they can cause a range of different symptoms and problems as they disrupt normal function of that organ.
Treatment for cancer that has spread usually includes some form of drug treatment that treats the cancer wherever it is in the body. Radiotherapy can be combined with the drug treatment to treat areas where the cancer cells are growing.
Most lumps in the breast are not serious
Cancer is the uncontrolled overgrowth of a group of cells
Another term for cancer is a malignant tumour
Cells from a malignant tumour, if left untreated, may continue to grow and eventually invade and spread to damage other tissues
As a cancer grows, some cancer cells may break away from the cancer and enter the bloodstream or the lymphatic system; this results in cancer cells spreading from the original cancer (the primary tumour) to form new cancers or secondary tumours in other organs – called metastases
Cancer cells that get into the lymphatic system can sometimes be felt as lumps under the arm in the lymph glands
Even if a cancer has spread, it can be treated