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What is breast cancer?

Breast cancer is the abnormal growth of cells in the breast. It usually starts in the lining of the breast ducts or lobules, and can grow into cancerous (malignant) tumours. Most breast cancers are found when they are invasive. This means that 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). Advanced breast cancer is when cancer cells have spread (metastasised) outside the breast to other parts of the body. This information covers early and locally advanced breast cancer only.

What are the different types of breast conditions and breast cancers?

Non-invasive breast conditions
These are precancerous conditions where the cells look like cancer cells but have not invaded nearby tissues. Also called carcinoma in situ.

ductal carcinoma in situ (DCIS)abnormal cells in the ducts of the breast; may develop into invasive breast cancer; treatment is the same as invasive breast cancer, but chemotherapy is not used.
lobular carcinoma in situ (LCIS)abnormal cells in the lobules of the breast; increases risk of developing cancer; needs regular mammograms or other scans to keep a check on; may be treated with hormone-blocking therapy or surgery in some cases.

Invasive breast cancers
Invasive means that the cancer cells have grown and spread into the surrounding tissue. The two main types of invasive breast cancer are named after the breast area that they start in.

invasive ductal carcinoma (IDC)starts in the ducts; about 80% of breast cancers are IDC.
invasive lobular carcinoma (ILC)starts in the breast lobules; about 10% of breast cancers are ILC.

Less common breast cancers include angiosarcoma, inflammatory breast cancer, medullary carcinoma, mucinous carcinoma, Paget disease of the nipple (or breast) and papillary carcinoma. Phyllodes tumour is a rare breast condition.

If invasive breast cancer spreads beyond the breast tissue and the nearby lymph nodes it is called advanced or metastatic breast cancer. For more information, call Cancer Council 13 11 20, or visit bcna.org.au or canceraustralia.gov.au.

How common is breast cancer?

There are about 20,000 people diagnosed with breast cancer in Australia every year.

Women – Breast cancer is the most common cancer in Australian women (apart from common skin cancers) – one in seven will be diagnosed in their lifetime.  Young women get breast cancer, but it is more common over the age of 40, and risk increases with age. In rare cases, pregnant or breastfeeding women get breast cancer – so see a doctor about any persistent lump noticed during pregnancy.

Men – About 160 Australian men are diagnosed with breast cancer each year — most aged over 50. It is treated in the same way as for women. Visit breastcancerinmen.canceraustralia.gov.au for specific information, or download Men get breast cancer too from Breast Cancer Network Australia.

Transgender, non-binary and gender-diverse – Any transgender woman taking medicines to boost female hormones and lower male hormones has an increased risk of breast cancer (compared to a man). A transgender man, who has had breasts removed in a nipple-sparing mastectomy (usually called top surgery), can still get breast cancer – though the risk is very low. This is thought to be because small amounts of breast tissue may remain after surgery.

Does breast cancer run in families?

Most people with breast cancer don’t have a family history, but a small number may have inherited a gene fault (also called a mutation or pathogenic variant)  that increases their breast cancer risk.

BRCA1 and BRCA2 – These are the most common gene mutations linked to breast cancer. Women in families with BRCA1 or BRCA2 are at increased risk of breast and ovarian cancers. Men in families with BRCA2 may be at increased risk of breast and prostate cancers.

Other types – These include BARD1, BRIP1, NF1, RAD51C, CDH1, PTEN, STK11, TP53, PALB2, ATM and CHEK2. More gene mutations linked to breast cancer are being found all the time.

To find out if you have inherited a gene mutation, talk to your doctor or breast cancer nurse about visiting a family cancer clinic or genetic oncologist. In  particular, women diagnosed before 40, those with triple negative breast cancer, and men with breast cancer should ask for a referral. Genetic testing is useful for people with a high chance of a gene fault, as it may help to work out the best treatment options. Medicare usually pays for testing if you have breast cancer and an increased chance of a mutation.

Featured resources

Breast Cancer - Your guide to best cancer care

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Understanding Breast Cancer

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This information is reviewed by

This information was last reviewed July 2022 by the following expert content reviewers: A/Prof Elisabeth Elder, Specialist Breast Surgeon, Westmead Breast Cancer Institute and The University of Sydney, NSW; Collette Butler, Clinical Nurse Consultant and McGrath Breast Care Nurse, Cancer Support Centre, Launceston, TAS; Tania Cercone, Consumer; Kate Cox, 13 11 20 Consultant, Cancer Council SA; Dr Marcus Dreosti, Radiation Oncologist and Medical Director, GenesisCare, SA; Dr Susan Fraser, Breast Physician, Cairns Hospital and Marlin Coast Surgery Cairns, QLD; Dr Hilda High, Genetic Oncologist, Sydney Cancer Genetics, NSW; Prof David W Kissane AC, Chair of Palliative Medicine Research, The University of Notre Dame Australia, and St Vincent’s Hospital Sydney, NSW; Prof Sherene Loi, Medical Oncologist, Peter MacCallum Cancer Centre, VIC; Dr W Kevin Patterson, Medical Oncologist, Adelaide Oncology and Haematology, SA; Angela Thomas, Consumer; Iwa Yeung, Physiotherapist, Princess Alexandra Hospital, QLD.