Breast cancer

Breast cancer arises from cells within the breast that accumulate changes to their DNA (‘genetic mutations’) that make them grow in an uncontrolled manner.

The structure of the breast is designed to produce and secrete milk from the nipple. Most breast cancers arise from cells in the breast ducts, which normally transport milk to the nipple. Some cancers develop from cells in the milk-producing lobules. It is rare for cancers to come from other structures in the breast such as fat or lymphatic vessels.

Breast cancers begin as a small, confined tumour, but can grow and spread throughout the breast. Early growths that are ‘pre-invasive’ as they have not left the ducts are termed DCIS (for ‘Ductal Carcinoma In Situ’). Invasive cancers are often described as ductal or lobular, based on their appearance down the microscope.

Some breast cancer cells may develop further changes that allow them to escape from the breast. They travel through lymphatic vessels to lymph nodes, or spreading through the blood to other organs, a process called ‘metastasis’.

Most breast cancers arise ‘spontaneously’, with no identifiable cause. Around five per cent of Australian breast cancer cases are ‘hereditary’, meaning the patient carries an inherited breast cancer risk gene, such as BRCA1 or BRCA2. This puts them at elevated risk of breast and ovarian cancer.

Other factors that increase a person’s risk of developing breast cancer include:

• Gender: females are at a much higher risk developing breast cancer, but breast cancer can occur in men
• Older age: like many cancers, the risk of developing breast cancer increases with age – about 80% arise after age 50
• Exposure of breast cells to female hormones
• Excessive alcohol consumption
• Obesity
• Exposure to high doses of radiation

Breast cancers that are confined to the breast, or have not spread beyond the lymph nodes can often be cured. Treatment depends on the precise tumour features and may include:

• Surgery
• Radiation therapy
• Chemotherapy
• Hormonal (endocrine) therapy, that blocks the action of oestrogen

Metastatic breast cancer, which has spread further in the body, is often treated with chemotherapy or hormonal therapy, again depending on the tumour and the patient.

For some types of breast cancer, treatments are designed to specifically target particular molecules that are promoting cancer growth. An example is therapy that targets HER2, a protein which is overproduced in about 15-20% of breast cancer. More detailed information about breast cancer treatment can be found at the Cancer Australia website.

WEHI researchers are not able to provide specific medical advice specific to individuals. If you have breast cancer and wish to find out more information about clinical trials, please visit Cancer Australia or Breast Cancer Network Australia clinical trials, or consult your medical specialist.