About breast cancer

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

Learn more about:

• What is breast cancer?
• The breasts
• How common is breast cancer
• What are the different types of breast conditions?
• What causes breast cancer?
• Does breast cancer run in families?

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 section covers early and locally advanced breast cancer only.

The breasts

The breasts sit on top of the upper ribs and a large chest muscle. They cover the area from the collarbone (clavicle), to the armpit (axilla) and across to the breastbone (sternum). Some breast tissue extends into the armpit and is called the axillary tail.

Female breasts are mostly made up of:

• lobes – each breast has 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 when breastfeeding
• fatty/fibrous tissue – all breasts contain some fatty or fibrous tissue (including connecting tissue called stroma), no matter what their size.

Most younger women have dense or thicker breasts, because they contain more lobules than fat. Male breasts have ducts and fatty/fibrous tissue. They contain no, or only a few, lobes and lobules.

The breasts (diagram)

The lymphatic system

The lymphatic system is an important part of the immune system, and protects against disease and infection. Working like a drainage system, it removes fluid from body tissues back into the blood. It is made up of a network of thin tubes called lymph vessels. These lymph vessels connect to groups of small, bean-shaped lymph nodes (or glands).

There are lymph nodes throughout the body, including in the armpit, neck, abdomen, groin and near the breastbone. The first place breast cancer cells usually spread to is the axillary lymph nodes in the armpit.

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. 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, 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.

What are the different types of breast conditions?

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.

Invasive breast cancer

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.

Less common types of breast cancer

These 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.

Advanced or metastatic breast cancer

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 Breast Cancer Network Australia or Cancer Australia.

What causes breast cancer?

Many factors can increase your risk of breast cancer, but they do not mean that you will develop it. You can also have none of the known risk factors and still get breast cancer. If you are worried, speak to your doctor. For more on this, see Cancer Australia’s Breast Cancer Risk Factors or petermac.org/iprevent.

	Personal factors Being female is the biggest risk factor – 99% of breast cancer cases are diagnosed in women. Risk increases with age for both men and women. About three quarters of breast cancer cases are in women over the age of 50. Free breast screening is available. Dense breast tissue (as seen on a mammogram) increases your risk. Breast implants or breast augmentation does not increase your risk of breast cancer.
	Lifestyle factors Being overweight or gaining weight after menopause. Losing weight to a health range can lower this. Drinking alcohol – the more that you drink, the higher your risk. If you choose to drink, the alcohol guidelines suggest you drink no more than 10 standard drinks in a week, and no more than 4 standard drinks on any one day. Not getting enough exercise or not being physically active. Smoking tobacco may increase your risk.
	Family history About 5–10% of breast cancers are due to an inherited breast cancer gene such as BRCA1 or BRCA 2. Most people with breast cancer do not have a strong family history. However, having several close relatives (e.g. mother, sister, aunt) on the same side of the family who have had breast or ovarian cancer may increase your risk. Several close relatives on the same side of the family with prostate or pancreatic cancer may increase your risk.
	Hormonal factors Using menopause hormone therapy (MHT) containing both oestrogen and progesterone, for long periods of time and over many years. Taking the pill (oral contraceptive) for a long time (small increase). Using some hormonal IUDs for a long time (small increase). You or your mother using diethylstilboestrol (DES) during pregnancy. Transgender women taking gender-affirming hormones for more than 5 years.
	Medical history Having been previously diagnosed with breast cancer, LCIS or DCIS. Some non-cancerous conditions of excessive growth of breast cells (hyperplasia). Having radiation therapy to the chest area for Hodgkin lymphoma. Males with a rare genetic syndrome called Klinefelter syndrome. Those with this syndrome have three sex chromosomes (XXY) instead of the usual two (XY).
	Reproductive factors Never having given birth may increase risk. Starting your first period (menstruating) before the age of 12 may increase your risk. Being older than age 30 when you gave birth to your first child increases your risk. Not having ever breastfed may increase your risk. Going through menopause after the age of 55 may increase your risk.

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.

→ READ MORE: Breast cancer symptoms