What is breast cancer?
Breast cancer is the abnormal growth of the cells lining the breast ducts or lobules. These cells grow uncontrollably and have the potential to spread to other parts of the body. Both women and men can develop breast cancer, although breast cancer is rare in men. Most breast cancers are found when they are invasive. Invasive breast cancer means the cancer has spread from the breast ducts or lobules into the surrounding breast tissue.
The breasts
Women and men both have breast tissue.
In women, breasts are mostly made up of lobes, lobules and ducts:
- Lobes – Each breast is divided into 12-20 sections called lobes.
- Lobules – Each lobe contains glands that produce milk. These milk glands are called lobules.
- Ducts – The lobes and lobules are connected by fine tubes called ducts. The ducts carry milk to the nipples.
In men, breast tissue has ducts but few or no lobes and lobules.
Both female and male breasts also contain fibrous and fatty tissue. Some breast tissue extends into the armpit (axilla). This is known as the axillary tail of the breast.
Breast cancer and the lymphatic system
The lymphatic system is an important part of the immune system. It protects the body against disease and infection. It is made up of a network of thin tubes called lymph vessels that are found throughout the body. Lymph vessels connect to groups of small, bean-shaped structures called lymph nodes or glands.
Lymph nodes are found throughout the body, including in the armpits, breastbone (sternum), neck, abdomen and groin. The lymph nodes in the armpit (axillary lymph nodes) are often the first place cancer cells spread to outside the breast. During surgery for breast cancer (or, sometimes, in a separate operation), some or all of the lymph nodes will be removed and examined for cancer cells. See information about surgery to remove lymph nodes.
What are the different types of invasive breast cancer?
The main types of invasive breast cancer are:
- invasive ductal carcinoma (IDC) – starts in the ducts and accounts for about 80% of breast cancers
- invasive lobular carcinoma (ILC) – starts in the lobules and makes up about 10% of breast cancers.
Less common types include inflammatory breast cancer and Paget’s disease of the nipple.
What is carcinoma in situ?
Sometimes tests find abnormal cells in the breast known as carcinoma in situ. These cells usually do not cause any symptoms and cannot spread to the lymph nodes or around the body as invasive breast cancer cells can. However, they may eventually turn into invasive breast cancer. There are two main types of carcinoma in situ in the breast:
Ductal carcinoma in situ (DCIS)
Abnormal cells in the ducts of the breast. DCIS is considered non-invasive breast cancer and usually develops into invasive breast cancer over time. In most cases, DCIS is treated in the same way as early invasive breast cancer.
Lobular carcinoma in situ (LCIS)
Abnormal cells in the lobules of the breast. This is not cancer, but increases the risk of developing cancer in either breast. However, most women with LCIS won’t develop breast cancer. If you have LCIS, you will usually have regular screening mammograms or other scans. Some less common types of LCIS may need surgery.
DCIS and LCIS are very rare in men.
Breast cancers are also categorised according to whether they are sensitive to hormones (hormone receptor status), have high levels of growth factors (HER2 positive) or are none of these (triple negative). See information about these categories.
What are the risk factors?
In most people, the exact cause of breast cancer is unknown, but some factors can increase the risk. Most people with breast cancer have no known risk factors, aside from getting older. Having risk factors does not necessarily mean you will develop breast cancer.
In women, risk factors include:
- older age
- a strong family history, with several first-degree relatives (e.g. mother, sister) diagnosed with breast cancer and/or a particular type of ovarian cancer. However, most women diagnosed with breast cancer do not have a family history
- inheriting a mutation in the BRCA1 or BRCA2 genes (see below) – more common with Ashkenazi Jewish heritage
- a previous diagnosis of breast cancer or ductal carcinoma in situ (DCIS)
- a past history of particular non-cancerous breast conditions, such as lobular carcinoma in situ (LCIS) or atypical ductal hyperplasia (abnormal cells in the lining of the milk ducts)
- regularly drinking alcohol
- being overweight after menopause
- a lack of physical activity
- having had radiation therapy to the chest for Hodgkin disease, especially if diagnosed under 30
- long-term hormone replacement therapy (HRT) use (slight increase in breast cancer risk).
Having children and breastfeeding can both slightly reduce breast cancer risk.
In men, risk factors include:
- older age
- a strong family history, with several first-degree relatives (male or female) who have had breast cancer; a relative diagnosed with breast cancer under the age of 40; or several relatives with ovarian or colon cancer
- inheriting a mutation in the BRCA1 or BRCA2 genes
- a rare genetic syndrome called Klinefelter syndrome – men with this syndrome have three sex chromosomes (XXY) instead of the usual two (XY).
Inherited breast cancer gene
Most people diagnosed with breast cancer do not have a family history of the disease. However, a small number of people have inherited a gene fault that increases their breast cancer risk.
Everyone inherits a set of genes from each parent, so they have two copies of each gene. Sometimes there is a fault in one copy of a gene. This fault is called a mutation.
The two most common gene mutations that are linked to breast cancer are on the BRCA1 and BRCA2 genes. Women in families with an inherited BRCA1 or BRCA2 change are at an increased risk of breast and ovarian cancers. Men in these families may be at an increased risk of breast and prostate cancers.
People with a strong family history of breast cancer can attend a family cancer clinic for tests to see if they have inherited a gene mutation. For more information about genetic testing, talk to your doctor or breast care nurse, or call Cancer Council 13 11 20.
What are the symptoms?
Some people have no symptoms and the cancer is found during a screening mammogram (a low-dose x-ray of the breast) or a physical examination by a doctor.
If you do have symptoms, they could include:
- a lump, lumpiness or thickening, especially if it is in only one breast
- changes in the size or shape of the breast
- changes to the nipple, such as a change in shape, crusting, sores or ulcers, redness, a clear or bloody discharge, or a nipple that turns in (inverted) when it used to stick out
- changes in the skin of the breast, such as dimpling or indentation, a rash, a scaly appearance, unusual redness or other colour changes
- swelling or discomfort in the armpit
- persistent, unusual pain that is not related to your normal monthly menstrual cycle, remains after your period and occurs in one breast only.
Most breast changes aren’t caused by cancer. However, if you have symptoms, see your doctor without delay.
For an overview of what to expect during all stages of your cancer care, visit What to expect – Breast cancer. This is a short guide to what is recommended, from diagnosis to treatment and beyond.
How common is breast cancer?
Apart from non-melanoma skin cancer, breast cancer is the most common cancer found in women – it represents 28% of all cancers diagnosed in women. About 17,000 women are diagnosed with breast cancer each year, and one in eight will be diagnosed by the age of 85. 1
Although breast cancer can occur at any age, it is more common in women over 40. Almost 70% of breast cancers are diagnosed in women aged 40-69, and about 25% are diagnosed in women aged 70 and over. In rare cases, women are diagnosed during pregnancy.
Which health professionals will I see?
Your general practitioner (GP) will arrange the first tests to
assess your symptoms. If these tests do not rule out cancer, you’ll usually be referred to a specialist breast service for further tests.
If breast cancer is diagnosed, you will usually first see a breast surgeon who will consider treatment options. Often these will be discussed with other health professionals at what is known as a multidisciplinary team (MDT) meeting. During and after treatment, you will see a range of health professionals who specialise in different aspects of your care.
Health professionals you may see
| GP | assists you with treatment decisions and works in partnership with your specialists in providing ongoing care |
| breast physician | diagnoses breast cancer and coordinates treatment for breast cancer in some clinics |
| breast surgeon* | specialises in surgery and performs biopsies; some breast surgeons also perform breast reconstruction and plastic surgery procedures |
| oncoplastic breast surgeon* | specialises in using plastic surgery techniques to reconstruct breast tissue after surgery |
| reconstructive (plastic) surgeon* | performs breast reconstruction for women who have had a mastectomy |
| anaesthetist* | administers anaesthetic before surgery and monitors you during the operation |
| pathologist* | examines cells and tissue samples that are removed from the breast to work out the type and extent of the cancer |
| breast care nurse | provides information, support and referral to women affected by breast cancer during and after treatment |
| nurse | administers drugs and provides care, information and support throughout treatment |
| radiologist* | analyses x-rays, mammograms, ultrasounds and other scans |
| radiation oncologist* | treats cancer by prescribing and coordinating a course of radiation therapy |
| radiation therapist | plans and delivers radiation therapy |
| medical oncologist* | treats cancer with drug therapies such as chemotherapy, hormone therapy, targeted therapy and immunotherapy |
| lymphoedema practitioner | educates people about lymphoedema prevention and management, and provides treatment if lymphoedema occurs; often a physiotherapist |
| dietitian | recommends an eating plan to follow during treatment and recovery |
| exercise physiologist | prescribes exercise to help people with medical conditions improve their overall health, fitness, strength and energy levels |
| physiotherapist, occupational therapist | assist with physical and practical problems, including restoring movement and mobility after treatment, and recommending aids and equipment |
| social worker | links you to support services and helps you with emotional, practical or financial issues |
| genetic counsellor | provides advice for people with a strong family history of breast cancer or with a genetic condition linked to breast cancer |
| psychiatrist*, psychologist, counsellor | help you manage your emotional response to diagnosis and treatment |
*Specialist doctor