Information about breast cancer

The following information is a brief description of some breast cancer basics. There are many websites available with more comprehensive information and we always recommend discussing your case with your medical professionals as everybody is unique.

What is cancer?

Cancer is a disease of the body's cells. Normally, the body's cells grow and divide in an orderly way, allowing your body to grow and to heal after an injury. Occasionally, some cells behave in an abnormal way and grow into a lump called a tumour. Tumours can be benign (not a cancer) or malignant (a cancer). Benign tumours do not spread to other parts of the body.

What is breast cancer?

Breast Cancer is a malignant tumour which starts within the breast tissue. The majority of breast cancers begin in the milk ducts (intraductal cancers). A small number start in the milk sacs or lobules (lobular cancers). Within these two groups there are different types of breast cancer. Some grow very slowly, others develop more rapidly. Breast cancer can spread to the lymph glands and to other parts of the body such as the bones and liver.

How comon is breast cancer?

Apart from skin cancer, breast cancer is the most common cancer in women. One in nine New Zealand women will develop breast cancer during their lives. About 2000 women are diagnosed each year. Although unusual, men can develop breast cancer (approximately 1% of all breast cancers occur in men). Click on the link below to hear one man's story of breast cancer.

What causes breast cancer?

The cause of breast cancer is unknown. However, it is most unlikely that there is one single cause. A number of factors, some known and many unknown, probably work together to trigger its growth. Breast cancer usually occurs in women over 50 and all women are at risk as they grow older. Although breast cancer does occur in women under 50, increasing age is the main factor influencing the risk of getting breast cancer. The factors listed below also seem to put women at slightly higher risk. However, they explain only a small number of breast cancer cases.

  • Women with a strong family history of breast cancer have an increased chance of getting breast cancer and a 60% increased risk of ovarian cancer. The increase in risk can be very small to quite large (only 5 – 10% of all breast cancers are hereditary), depending upon the number of relatives affected, the age of the relatives when their breast cancer was found, and the type of breast cancer they had.
  • Women who have already had breast cancer do have a slightly higher chance of a new breast cancer developing in their other breast.
  • Researchers are looking into a number of factors which may influence the development of breast cancer. Because breast cancer is more common in certain countries, lifestyle factors, such as diet are thought to be important (Did you know that two glasses of wine each day could give you an increased risk of 41%?).
  • Hormone changes linked with pregnancy and menopause also appear to have an effect. None of these factors are certain enough though, to predict who will develop breast cancer.
Risks linked with the pill suggest a possible increased risk of 10% and women on HRT can have an increased risk of up to 35%.

Helpful links

There is a lot of information out there and starting to google 'breast cancer' can bring up a myriad of different sources of information. Hard to know what is reliable and what is not and it can be a bit scary reading some of what is on the internet. Here are some websites you may find useful:

MacMillan Cancer Support is a UK site with loads of information about cancer in general and specific information about breast cancer.

Health Navigator NZ helps you find reliable and trustworthy information and self help resources about breast cancer.

Better Health Channel is a Victorian (Australian) website and has information about breast cancer.

NZ Breast Cancer Foundation is a national organisation based in Auckland with a focus on research and education. It is packed full of useful information.


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