Breast cancer is an abnormal growth of cells in the breast. There are different types of breast cancer, but they all start in the milk ducts or the milk lobules (milk-producing glands). The cancer may grow into surrounding tissues and spread to other organs of the body.
Breast cancer is the most common form of cancer in women in Australia. Around one woman in every eight is diagnosed with breast cancer before the age of 85, according to government statistics. However, it is important to remember many more women die of heart disease and stroke in Australia than die of breast cancer.
Who is most at risk of developing breast cancer?
The main risk factors for breast cancer are the ones you can't change:
- being a woman
- getting older – over 50-75% of breast cancers occur in women over the age of 50
- having a strong family history of breast cancer
- inheriting a faulty gene that increases the risk.
Of all breast cancers, 90-95% have nothing to do with family history. However, having one or more first-degree (parent, sibling or child) or second-degree (eg, grandparent, uncle, aunt) relatives on the same side of the family with breast cancer increases your risk.
Around 5-10% of breast cancers occur in women whose families have a gene mutation that is passed down through the family and puts them at greater risk of developing breast cancer.
Other factors that may increase the risk include:
- having dense breasts
- being overweight
- drinking alcohol
- radiation to chest and face before the age of 30
- exposure to Diethylstilboestrol (DES), a synthetic form of oestrogen
- using the oral contraceptive pill (according to the Cancer Council of Australia, it is a slightly higher risk, which disappears within 10 years of stopping the pill)
- using menopause hormone therapy, or MHT (formerly called hormone replacement therapy, or HRT)
(again, a very slight risk, which is lost within five years of stopping MHT).
You can read more about the risk factors at:
If you are concerned about your risk of breast cancer, talk to your doctor.
Breast cancer diagnosis
Breast changes that may indicate breast cancer include:
- a new lump or lumpiness, especially if it's in only one breast
- a change in the size or shape of the breast
- a change to the nipple, such as crusting, ulcer, redness or inversion
- a nipple discharge that occurs without squeezing
- a change in the skin of the breast, such as redness, dimpling or puckering
- an unusual pain that doesn't go away.
If you have any of these symptoms, see your doctor, who will examine you and refer you to a breast specialist. The specialist will conduct tests to determine whether your symptoms are benign (harmless) or cancerous. They will usually:
- examine your breasts
- take a mammogram or an ultrasound of your breast
- conduct a needle biopsy, where the radiologist inserts a needle into your breast with guidance of a mammogram or ultrasound machine, and takes a small sample of tissue to test for cancer.
If any of these three tests (known as the triple test) causes concern, your specialist will recommend further investigation and perhaps removing the lump or suspicious area.
Take any new symptoms seriously and see your doctor promptly. Early diagnosis is the key to successful treatment.
Size & breast cancer
The risk of developing breast cancer has nothing to do with the size of your breasts. Women who are overweight tend to have larger breasts, but their breast size is not relevant to their breast cancer risk.
Weight gain and breast cancer
In a number of studies, higher body mass index (BMI) and postmenopausal weight gain have been associated with a higher risk of developing breast cancer. The studies also found:
- women who weighed more than 80kg had a 25% higher risk of developing breast cancer compared to those weighing less than 60kg
- women who had gained 10kg or more since menopause had an 18% higher risk of developing breast cancer compared with women who maintained their weight.
These findings are likely to be because women who have more fat tissue have higher circulating levels of oestrogen. Fat tissue produces oestrogen, which is linked to breast cancer.
Breast injury & breast cancer
Breast injury may cause scarring or damage to the fatty tissue, but it is not known to cause breast cancer.
Injury can cause tenderness, and many women are concerned that pain may be a feature of breast cancer. However, breast tenderness is usually due to benign (non-cancerous) breast disease, such as those detailed earlier in this section. These conditions do not increase the risk of breast cancer.
Breast cancer & menopausal symptoms
Menopausal symptoms and breast cancer are associated for a number of reasons:
- Cancer treatment can cause ovaries to fail and trigger menopause
- You may be in menopause when you are diagnosed with breast cancer
- Adjuvant endocrine (hormone) therapy, which works to prevent breast cancer recurrence, can cause menopausal symptoms
- Stopping menopause hormone therapy (MHT) when your breast cancer diagnosis is made can cause menopausal symptoms that may have been masked by MHT.
Menopausal symptoms may start abruptly with breast cancer treatment or advance slowly; there is no way of predicting how menopause will affect each woman. More information is available in our pages on menopause after cancer.
Breast cancer & osteoporosis
Women who develop breast cancer may be at risk of developing osteoporosis, a condition in which bones become fragile and brittle. It's important for women who have been diagnosed with breast cancer to check their bone health, especially if they have other risk factors for osteoporosis.
For women who are diagnosed with osteoporosis, there are therapies available that can treat this condition. Weight-resistant exercises, adequate calcium in your diet and adequate vitamin D are important parts of managing osteoporosis.
Premenopause & osteoporosis
Premenopausal women undergoing treatment for cancer often become prematurely menopausal because chemotherapy can lead to ovarian failure.
Once the ovaries stop functioning, bone density loss occurs, particularly in the spine. In the first 12 months after chemotherapy, bone loss in the spine is about 3-4%. Even though this bone loss may occur, it does not necessarily lead to osteoporosis.
If ovarian failure does not occur after chemotherapy, bone density or strength tends to remain stable.
Premenopausal women who are given tamoxifen (sold as Nolvadex, Genox, Tamosin and Tamoxen) also experience a progressive loss of bone density from the spine of about 1.4% per year. Tamoxifen works by partially suppressing the body's production of oestrogen. It has anti-oestrogen effects in the breast, but continues to have oestrogen-like effects in bone, which protects against bone loss.
Postmenopause & osteoporosis
The effect of breast cancer treatment on bone density for postmenopausal women is slightly different from that of premenopausal women. Chemotherapy for postmenopausal women results in loss of bone density or strength.
Tamoxifen has a positive effect on bone density in postmenopausal women, resulting in an increase in bone density in the spine of about 1.2% per year. However, a report noted a slightly increased rate of fracture in this group compared to the normal population, despite the increases in bone density. More research is needed in this area.
Aromatase inhibitors & osteoporosis
Aromatase inhibitors are prescribed in Australia for postmenopausal women whose breast cancer has spread beyond the breast and lymph nodes. These drugs work by virtually suppressing all oestrogen production in the body. The studies with one of these drugs known as anastrozole (sold as Arimidex), has shown that it does lead to loss of bone density at the spine and hip. This effect seems to be more significant in women who are newly menopausal. There is also a very slightly increased risk of fracture for women taking this medication, although further research is needed in this area.
Breast cancer & mental health
About 50% of women with breast cancer experience depression and/or anxiety. Some women are depressed and anxious in the first years after breast cancer is diagnosed, and about 25% of women remain depressed four years after their diagnosis.
Younger women with breast cancer experience more physical symptoms, psychological distress and poorer sexual functioning compared to other breast cancer age groups.
The experience of depression and anxiety with breast cancer is often affected by:
- the stage you are dealing with – if a tumour has been removed or is shrinking, compared with if a tumour is growing or has returned
- the treatment you need – such as surgery or chemotherapy – and the demands this places on you psychologically
- the support you receive from family and friends
- whether you have previously experienced any depression or anxiety that might return when dealing with your breast cancer diagnosis and treatment.
When to see your doctor
If you have symptoms of anxiety and depression, please see your doctor, as there are a range of treatments available to help you.
Ding H, Field T.S. Bone health in postmenopausal women with early breast cancer: How protective is tamoxifen? Cancer Treatment Review. 2007 Oct;33(6):506-513
Miller L.E. Young Breast Cancer Survivors' Experiences of Uncertainty. Journal of Applied Communication Research.2015;43(4):429-449
Last updated 02 November 2018 — Last reviewed 30 October 2018
This web page is designed to be informative and educational. It is not intended to provide specific medical advice or replace advice from your health practitioner. The information above is based on current medical knowledge, evidence and practice as at October 2018.