About breast cancer

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

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 and nearby lymph nodes to other parts of the body. About 5% of cancers are advanced when breast cancer is first diagnosed.

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:

Most younger women have dense or thicker breasts because they contain more lobules than fat.

Male breasts have ducts and fatty/fibrous tissue. They usually 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, which protects against disease and infection. The lymphatic system drains excess fluid from body tissues into the blood. It is made up of a network of thin tubes called lymph vessels. These vessels connect to groups of small, bean-shaped lymph nodes (or glands).

There are lymph nodes throughout the body, including in the armpits, neck, abdomen, groin and chest (near the breastbone). The first place breast cancer cells usually spread to is the lymph nodes in the armpits (axillary lymph nodes) or to the lymph nodes near the breastbone (internal mammary lymph nodes).

How common is breast cancer?

About 20,700 people are diagnosed with breast cancer in Australia every year.

Women

In Australia, breast cancer is the most common cancer in women (apart from common skin cancers), with 1 in 8 women diagnosed by age 85. Young women can get breast cancer, but it is more common over the age of 40, and the risk increases with age.

In rare cases, pregnant or breastfeeding women can get breast cancer. See a doctor about any persistent lump noticed during pregnancy.

Men

About 220 men (most aged over 60) are diagnosed with breast cancer each year. It is treated in the same way as for women. For more information, visit breastcancerinmen.canceraustralia.gov.au or BCNA’s Breast cancer in men.

Transgender, non-binary and gender-diverse

Any transgender woman taking medicines to boost female hormones and lower male hormones has a higher breast cancer risk (compared with a man). A transgender man who has had breasts removed in a nipple-sparing mastectomy can still get breast cancer, although the risk is low.

For more on this, see LGBTQI+ people and cancer.

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

Non-invasive breast conditions

These are conditions where the abnormal cells have not invaded nearby tissues. Also called carcinoma in situ.

Invasive breast cancer

Invasive means that the cancer cells have grown and spread beyond the breast ducts/lobules and into the surrounding tissue. The 2 main types of invasive breast cancer are named after the breast area that they start in.

Less common types of breast cancer

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

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. 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. More than 3 in 4 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 do not increase breast cancer risk, but some implants are linked with a type of cancer called lymphoma. See the Australian government’s breast implant hub.
	Lifestyle factors Being overweight or gaining weight after menopause. Losing weight to a healthy range can lower this. Drinking alcohol – the more that you drink, the higher your risk. If you choose to drink, the Australian alcohol guidelines suggest you drink no more than 10 standard drinks a week, and no more than 4 standard drinks on any one day. Not getting enough exercise or not being physically active. Smoking tobacco.
	Family history About 5–10% of breast cancers are due to an inherited breast cancer gene such as BRCA1 or BRCA2. 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 Long-term use of menopausal hormone therapy (MHT) containing both oestrogen and progesterone. Taking the oral contraceptive pill (the pill) for a long time may slightly increase the risk. 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 (atypical ductal hyperplasia or ADH). Having radiation therapy to the chest area for Hodgkin lymphoma. Males with a rare genetic syndrome called Klinefelter syndrome. Those with this syndrome have 3 sex chromosomes (XXY) instead of the usual 2 (XY).
	Reproductive factors Never having given birth to a child. Starting your first period (menstruating) before the age of 12. Being older than age 30 when you gave birth to your first child. Never having breastfed a child. Going through menopause after the age of 55.

Does breast cancer run in families?

Most people with breast cancer do not have a strong family history, but a small number may have inherited a gene fault (also called a mutation) that increases their breast cancer risk.

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. Your specialist may also be able to order genetic tests.

In particular, women diagnosed before 40 years, those with triple negative breast cancer diagnosed before 60 years, and men with breast cancer should ask for a referral. Genetic testing is covered by Medicare for some, but not all, people; ask your doctor about this.

→ READ MORE: Breast cancer symptoms