Breast cancer in Australia
Breast cancer is the most common cancer affecting women in Australia.
About 1 in 7 women will be diagnosed with breast cancer by the age of 85. Breast cancer can also affect men. Around 1 in 688 men will be diagnosed by the age of 85.
In 2025 it is estimated that around 20,336 people in Australia were diagnosed with breast cancer. While diagnosis rates have increased, death rates from breast cancer have decreased. Around 92.7% of people diagnosed with breast cancer can live for 5 years or longer after diagnosis.
There are different types of breast cancer. Treatment depends on the type of breast cancer and the needs of each person.
Normal breast structures
The normal female breast is made up of 15 to 20 sections called lobes. Each lobe contains smaller parts called lobules.
These lobules are connected by tubes (ducts) that eventually join up and lead to main ducts at the nipple. The lobules are the milk producing parts of the breast.
The ducts help to take the milk to the nipple during breastfeeding. In between the ducts and lobules there is fat and fibrous tissue holding all the structures together.
The structure of a breast includes:
- lobules which produce milk
- milk ducts which are small tubes that carry milk from the lobules to the nipple during breastfeeding
- fat and fibrous tissue sit between the lobules and ducts and support the breast structure.
The lymphatic system and breast cancer
The lymphatic system helps remove waste from the body and supports the immune system. The lymphatic system comprises of:
- lymphatic vessels are similar to veins but carry a clear fluid called lymph that contains waste products and immune cells
- lymph nodes are small, bean-shaped glands that help fight infection
- most lymphatic vessels in the breast drain to the axillary (underarm) lymph nodes.
Breast cancer cells can enter lymphatic vessels and travel to nearby lymph nodes. If cancer cells grow in the axillary lymph nodes, they may cause swelling in the armpit. If cancer cells multiply in the lymph nodes this may increase the chance that cancer has spread to other parts of the body.
Diagnosis of breast cancer
Breast cancer is usually diagnosed using a core biopsy, where a small piece of tissue is removed from an abnormality in the breast that is felt as a lump and seen on breast imaging (e.g., ultrasound or mammogram).
A pathologist examines the biopsy under a microscope to confirm the diagnosis.
The pathology report will include:
- the type of invasive breast cancer or in situ carcinoma
- the cancer grade (grade 1, 2 or 3)
- whether hormone receptors or HER2 receptors are present on the tumour cells.
Types of breast cancer
There are different kinds of breast cancer depending on where the cancer cells grow which can be classified as non-invasive (carcinoma in situ) or invasive.
Carcinoma in situ refers to cancer cells which are confined to the ducts or lobules in the breast (non-invasive) and have not spread into the surrounding breast tissue.
There are different kinds of breast cancer depending on where the cancer cells grow which can be classified as non-invasive or invasive.
If non-invasive breast cancers are not treated, they may spread into surrounding breast tissue. When this happens, it becomes invasive breast cancer. There are two types of breast carcinoma in situ.
Ductal carcinoma in situ (DCIS) is an early form of breast cancer. It is the most common type of non-invasive breast cancer. where:
- cancer cells grow inside the milk ducts or lobules
- the cells have not spread outside the ducts into nearby breast tissue
- if DCIS is not treated, it can develop into invasive breast cancer.
Lobular carcinoma in situ (LCIS) is another early form of breast cancer confined to the ducts or lobules of the breast. It is:
- usually discovered on a biopsy performed to investigate a breast lump or abnormal finding on mammogram
- often that women with LCIS have an increased risk of developing invasive breast cancer in either breast.
Invasive breast cancers are those cancers which have spread outside the ducts and lobules. The most common type of breast cancer is invasive ductal carcinoma which accounts for more than 80% of breast cancers. Lobular carcinoma is another form of breast cancer which is seen in about 10% of patients.
Breast cancers are divided into 3 grades (grade 1, grade 2, or grade 3) and this will be seen in the pathology report of the core biopsy.
The core biopsy will also be tested by the pathologist to see if there are receptors present in the cancer cells that can help plan treatment.
Breast cancers may express hormone receptors such as oestrogen receptor (ER) and/or progesterone receptors (PR). A further test for HER2 (human epidermal growth factor receptor 2) will also be performed.
These results will appear in the pathology report and help to guide the best treatment for each patient.
Patient stories
These patient stories share real experiences of people affected by breast cancer.
