About 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.

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 on breast cancer in men, visit Cancer Australia or Breast Cancer Network Australia.

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. Learn more about LGBTQI+ people and cancer.

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 connective tissue called stroma), no matter 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 usually contain no, or only a few, lobes and lobules.

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).

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.

Ductal carcinoma in situ (DCIS)

• abnormal cells in the breast ducts
• may develop into invasive breast cancer
• treatment is similar to that for invasive breast cancer, but chemotherapy is not used

Lobular carcinoma in situ (LCIS)

• abnormal cells in the breast lobules
• does not develop into cancer but increases the risk of developing cancer, including in the other breast
• usually treated with surgery, and hormone therapy may be used
• more regular mammograms or other scans needed to check for any changes

Invasive breast cancers

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.

Invasive ductal carcinoma (IDC)

• starts in the breast 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 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.

If invasive breast cancer spreads beyond the breast tissue and the nearby lymph nodes, it is called advanced or metastatic breast cancer. See Advanced breast cancer, or visit Breast Cancer Network Australia.

Guides to Best Cancer Care

Find an overview of what to expect at every stage of breast cancer care. These are short guides to what is recommended, from diagnosis to treatment and beyond.

Which health professionals will I see?

You may be sent for tests after a screening mammogram, or your general practitioner (GP) may arrange tests to check your symptoms.

If these tests do not rule out cancer, you will usually be referred to a specialist or breast clinic. If breast cancer is diagnosed, you will see a breast surgeon or a medical oncologist, who will talk to you about your treatment options. Often these will be discussed with other health professionals at a multidisciplinary team (MDT) meeting. During and after treatment, you will see a range of health professionals who specialise in different aspects of your care. You may not see all members of the MDT.

Health professionals you may see

• GP – arranges initial tests to investigate symptoms; assists you with treatment decisions and works in partnership with your specialists in providing ongoing care when cancer is diagnosed
• breast physician – diagnoses breast cancer and other breast conditions, especially when initial test results are unclear; provides care and support during and after treatment
• radiologist – analyses mammograms, ultrasounds and other scans; performs fine needle and core biopsies to confirm diagnosis
• radiographer/sonographer – performs mammograms, breast ultrasound and other scans
• breast surgeon – diagnoses breast cancer, performs surgical (excisional) biopsies in some clinics; performs breast surgery; some breast surgeons also perform breast reconstruction; oncoplastic breast surgeons specialise in using plastic surgery techniques to reconstruct breast tissue after surgery
• reconstructive (plastic) surgeon – performs breast reconstruction after mastectomy
• radiation oncologist – treats cancer by prescribing and overseeing a course of radiation therapy
• medical oncologist – treats cancer with drug therapies such as chemotherapy, hormone therapy, targeted therapy and immunotherapy (systemic treatment)
• breast care nurse – provides breast cancer care; also provides information and facilitates referrals during and after treatment
• chemotherapy nurse – administers drugs and provides care, information and support throughout treatment
• anaesthetist – assesses your health before the operation, administers anaesthetic and looks after you during and after surgery; plans your pain relief
• radiation therapist – plans and delivers radiation therapy
• physiotherapist, exercise physiologist – help restore movement and mobility, and improve fitness and wellbeing
• occupational therapist – assists in adapting your living and working environment to help you resume usual activities after treatment
• lymphoedema practitioner – educates people about lymphoedema prevention and management, and provides treatment if lymphoedema occurs; is often a physiotherapist or occupational therapist
• social worker – links you to support services and helps you with emotional, practical and financial issues
• dietitian – helps with nutrition concerns and recommends changes to diet during treatment and recovery
• psychologist, counsellor – help you manage your emotional response to diagnosis and treatment
• genetic counsellor – provides advice for people with a strong family history of breast cancer or for people with a genetic condition linked to cancer
• sexual health counsellor – helps you manage the sexual side effects of cancer and its treatments