Breast Cancer – Cancer Council NSW

Breast Cancer – Cancer Council NSW

Breast Cancer – Cancer Council NSW (Austrailia)

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. (Breast Cancer – Cancer Council of New South Wales, Australia.)

I went for an ultrasound and while they were doing it, people just kept coming in and I thought, ‘Oh, okay, everyone’s taking a lot of interest in this.’ The biopsies then confirmed that it was cancer.

Read more of Anne’s story

This section, above all, covers early and locally advanced breast cancer (cancer that hasn’t spread beyond the breast tissue and nearby lymph nodes). Invasive breast cancer that has spread further is called advanced or metastatic.

Also, if you are looking for information about advanced breast cancer, inflammatory breast cancer or Paget’s disease of the nipple, then call Cancer Council 13 11 20, or visit the Breast Cancer Network of Australia or Cancer Australia.

Learn more about:

(Breast Cancer – Cancer Council)

The breasts

Women and men both have breast tissue.

In women, breasts mostly consist 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 also extends into the armpit (axilla). This is known as the axillary tail of the breast.

Breast Cancer - Cancer Council the breasts diagram

Breast cancer and the lymphatic system

The lymphatic system is certainly an important part of the immune system.

Therefore, it protects the body against disease and infection. The Lymphatic System is a network of lymph vessels, thin tubes, that exist throughout the body. Similarly, lymph vessels connect to groups of small, bean-shaped structures called lymph nodes or glands.

Lymph nodes exist throughout the body, and include the armpits, breastbone (sternum), neck, abdomen and groin. Consequently, the first place cancer cells spread to outside the breast is to the lymph nodes in the armpit (axillary lymph nodes). During surgery for breast cancer (or, sometimes, in a separate operation), doctors will remove and examine some or all of the lymph nodes for cancer cells. For more on this kind of surgery, see Removing lymph nodes.

(Breast Cancer – Cancer Council)

What is invasive breast cancer?

Most breast cancers are found when they are invasive. Furthermore, invasive breast cancer means the cancer has spread from the breast ducts or lobules into the surrounding breast tissue.

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.

In contrast, less common types include inflammatory breast cancer and Paget’s disease of the nipple.

(Breast Cancer – Cancer Council)

About carcinoma in situ?

Sometimes tests likewise find abnormal cells in the breast known as carcinoma in situ. These cells, in contrast, 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 (see Treatment).

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 Tests on breast cancer for information about these categories.

(Breast Cancer – Cancer Council)

What causes breast cancer?

In most people, the exact cause of breast cancer is unknown, but some factors can increase the risk. Furthermore, 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. However, most women diagnosed with breast cancer do not have a family history
  • inheriting a mutation in the BRCA1 or BRCA2 genes − 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 genes

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. You can also listen to our podcast on Genetic Tests and Cancer.

(Breast Cancer – Cancer Council)

Who gets breast cancer?

Apart from non-melanoma skin cancer, breast cancer is the most common cancer affecting Australian women – it represents 28% of all cancers 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.

Although breast cancer can occur at any age, it is more common in women over 40. Almost 70% of breast cancers affect women aged 40–69, and about 25% affect women aged 70 and over. In rare cases, women are diagnosed during pregnancy.

Also, breast cancer affects about 140 men in Australia each year, and most of these men are over 50. As a result, resources are available for men diagnosed with breast cancer – visit Cancer Australia’s website at breastcancerinmen.canceraustralia.gov.au.

This information was last reviewed in August 2018

Prof Christobel Saunders, Professor of Surgical Oncology and Head, Division of Surgery, The University of Western Australia, and Consultant Surgeon, Royal Perth, Fiona Stanley and St John of God Subiaco Hospitals, WA; Dr Marie-Frances Burke, Radiation Oncologist, Medical Director, Genesis CancerCare Queensland, QLD; Kylie Campbell, Breast Care Nurse and Clinical Lead, Murraylands, McGrath Foundation, SA; Carmen Heathcote, 13 11 20 Consultant, Cancer Council Queensland, QLD; Annmaree Mitchell, Consumer; Sarah Pratt, Nurse Coordinator, Breast Service, Peter MacCallum Cancer Centre, VIC; Dr Wendy Vincent, Breast Physician, Chris O’Brien Lifehouse and Royal Hospital for Women, Randwick, NSW, and Clinical Director BreastScreen NSW, Royal Prince Alfred Hospital, NSW; A/Prof Nicholas Wilcken, Director of Medical Oncology, Westmead Hospital, and Co-ordinating Editor, Cochrane Breast Cancer Group, NSW.

We also thank the health professionals, consumers and editorial teams who have worked on previous editions of this title. This booklet is funded through the generosity of the people of Australia.


The cancer information on this website is based on the Understanding Cancer series booklets published by Cancer Council. This information is reviewed and updated every two years or as new information comes to hand. Cancer Council works with cancer doctors, specialist nurses or other relevant health professionals to ensure the medical information is reliable and up to date. Consumers also check the booklets to ensure they meet the needs of people with cancer. Before commencing any health treatment, always consult your doctor. This information is a general introduction, so please consult your own doctor’s or health professional’s advice. We take care to ensure that the information is accurate at the time of publication.

(Breast Cancer – Cancer Council)

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