Breast cancer

In this section we talk about about early and locally advanced breast cancer.

Learn more about:

What is breast cancer?
The breasts
Who gets breast cancer?
What are the different types of breast conditions?
What causes breast cancer?
How common is breast cancer

What is breast cancer?

Breast cancer is the abnormal growth of the cells lining the breast ducts or lobules. These abnormal cells have the potential to spread to other parts of the body.

Most breast cancers are found when they are invasive. This means the cancer has spread from the breast ducts or lobules into the surrounding breast tissue. Invasive breast cancer can be early, locally advanced or advanced (metastatic).

The breasts

Everyone has breast tissue.

Female breasts are mostly made up of:

lobes – each breast is divided into 12–20 sections called lobes
lobules – each lobe contains glands that can produce milk; these milk glands are called lobules or glandular tissue
ducts – the lobes and lobules are connected by fine tubes called ducts; the ducts carry milk to the nipples.

Male breast tissue has ducts but few or no lobes and lobules.

All breasts also contain fibrous and fatty tissue. Some breast tissue extends into the armpit (axilla).

Most younger females have dense breasts, because they have more glandular tissue than fat in them.

The breasts (diagram)

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, neck, abdomen and groin, and behind the breastbone (sternum). The lymph nodes in the armpit (axillary lymph nodes) are often the first place cancer cells spread to outside the breast.

Who gets breast cancer?

Anyone can develop breast cancer. While it is much more common in women, men can also get breast cancer. Breast cancer in males is usually diagnosed and treated in the same way as it is for females.

For more information for men diagnosed with breast cancer, visit breastcancerinmen.canceraustralia.gov.au or download BCNA’s Men get breast cancer too booklet.

Transgender and gender-diverse people can also get breast cancer.

A transgender woman who is taking medicines to boost female hormones and lower male hormones may have an increased risk of developing breast cancer.

A transgender man who has a mastectomy is still at risk of developing breast cancer. This is likely due to small amount of breast tissue that may remain after surgery.

What are the different types of breast conditions?

Non-invasive breast conditions

Also called carcinoma in situ. These are a precancerous condition where the cells look like cancer cells, but have not invaded nearby tissues.

ductal carcinoma in situ (DCIS)	abnormal cells in the ducts of the breast may develop into invasive breast cancer treated in a similar way to invasive breast cancer, but chemotherapy is not used
lobular carcinoma in situ (LCIS)	abnormal cells in the lobules of the breast increases the risk of developing cancer in either breast needs regular mammograms or other scans

Invasive breast cancer

There are two main types of invasive breast cancer. They are named after the area of the breast they start in.

invasive ductal carcinoma (IDC)	starts in the ducts accounts for about 80% of breast cancers
invasive lobular carcinoma (ILC)	starts in the lobules makes up about 10% of breast cancers

Less common types of breast cancer

These include inflammatory breast cancer, Paget’s disease of the nipple, medullary carcinoma, mucinous carcinoma and papillary carcinoma.

Advanced or metastatic breast cancer

If invasive breast cancer spreads beyond the breast tissue and nearby lymph nodes, it is called advanced or metastatic breast cancer.

For more information on less common types of breast conditions or advanced breast cancer, call Cancer Council 13 11 20, or visit Breast Cancer Network Australia or Cancer Australia.

What causes breast cancer?

Many factors can increase your risk of breast cancer. But having risk factors does not mean that you will develop breast cancer. For more on this, see Cancer Australia’s Breast Cancer Risk Factors or petermac.org/iprevent.

Female specific

personal factors	older age; dense breast tissue as seen on a mammogram
lifestyle factors	being overweight or gaining weight after menopause; drinking alcohol every day; not being physically active
medical factors	using menopause hormone therapy (MHT) that contains both oestrogen and progestogen; taking the pill for a long time (small increase); taking diethylstilboestrol (DES) during pregnancy; having radiation therapy to the chest for Hodgkin lymphoma; having atypical ductal hyperplasia or proliferative disease without atypia; previous diagnosis of LCIS or DCIS
reproductive factors	starting first period younger than 12; being older than 30 at the birth of first child; not giving birth; not having breastfed; going through menopause after 55
family history factors	a family history of breast cancer and/or a particular type of ovarian cancer in first-degree relatives (e.g. mother, sister) on the same side of the family, especially if diagnosed at a young age

Male specific

personal factors	older age
medical factors	a rare genetic syndrome called Klinefelter syndrome – males with this syndrome have three sex chromosomes (XXY) instead of the usual two (XY)
family history factors	a family history, with several first-degree relatives (male or female) who have had BRCA2 breast cancer; a relative diagnosed with breast cancer under the age of 40; or several relatives diagnosed with ovarian, colon or prostate cancer

Inherited breast cancer gene

Most people diagnosed with breast cancer don’t have a family history of the disease. However, a small number of people may 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 or pathogenic variant.

The two most common gene mutations linked to breast cancer are the BRCA1 and BRCA2 genes. Other types include CDH1, PTEN, STK11, TP53, PALB2, ATM and CHEK2. Women in families with an inherited BRCA1 or BRCA2 change are at increased risk of breast and ovarian cancers. Men in families with an inherited BRAC2 change may be at an increased risk of breast and prostate cancers.

To find out if you have inherited a gene mutation, you can visit a family cancer clinic. Talk to your doctor or breast cancer nurse.

How common is breast cancer?

Breast cancer is the most common cancer in Australian women (apart from common skin cancers). 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 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. About 150 men are diagnosed with breast cancer in Australia each year, and most of these men are over 50.

This information was last reviewed in July 2020. View who reviewed this content.

Prof Bruce Mann, Professor of Surgery, The University of Melbourne, and Director, Breast Tumour Stream, Victorian Comprehensive Cancer Centre, VIC; Dr Marie Burke, Radiation Oncologist, and Medical Director GenesisCare Oncology, QLD; Dr Susan Fraser, Breast Physician, Cairns Hospital and Marlin Coast Surgery Cairns, QLD; Ruth Groom, Consumer; Julie McGirr, 13 11 20 Consultant, Cancer Council Victoria; A/Prof Catriona McNeil, Medical Oncologist, Chris O’Brien Lifehouse, NSW; Dr Roya Merie, Staff Specialist, Radiation Oncology, Liverpool Cancer Therapy Centre, Liverpool Hospital, NSW; Dr Eva Nagy, Oncoplastic Breast Surgeon, Sydney Oncoplastic Surgery, NSW; Gay Refeld, Clinical Nurse Consultant – Breast Care, St John of God Subiaco Hospital, WA; Genny Springham, Consumer.

View the Cancer Council NSW editorial policy.