Different types of breast cancer

Breast cancer is a disease where abnormal breast cells grow out of control and form tumours.

There are different types of breast cancer, which require different treatments. There are 2 main types of breast cancer: invasive and non-invasive.¹

Non-invasive breast cancers are abnormal cells in the milk ducts (breast lobules). They haven't invaded normal breast tissue. These are called 'carcinoma in situ' and are sometimes also known as 'pre-cancers'.

Types of non-invasive breast cancers include:

The most common kind of non-invasive breast cancer, DCIS is classified by abnormal changes in the milk ducts. It hasn't spread into any other surrounding breast tissue. This non-life-threatening form of breast cancer can increase your risk of developing invasive breast cancer later in life. Your doctor will advise you about more frequent screenings and check-ups.

This is when abnormal cells are in the breast lobules (glands that make milk). Although it's classified as a type of breast cancer, it's actually a benign breast change. However, it may increase the risk of invasive breast cancer later in life. Talk to your doctor about frequent screenings and check-ups.

Invasive breast cancers mean the cancer cells have spread outside the breast ducts into surrounding breast tissue. Breast cancer can spread through the lymphatic system, the bloodstream, or when cancer cells invade nearby tissues.

Types of invasive breast cancers include:

This accounts for around 80% of all invasive breast cancers.² It refers to cancer that began in the milk ducts and has spread into the surrounding breast tissue. It can spread to lymph nodes and other parts of the body.

The second most common type of invasive breast cancer,³ this starts in the breast and spreads to other parts of the body. As with IDC, it can spread to lymph nodes and other parts of the body.

Other less common types of breast cancers include Paget's disease of the nipple, medullary carcinoma, mucinous carcinoma, papillary carcinoma and inflammatory breast cancer.

Inflammatory breast cancer (IBC) doesn't look like typical breast cancer. It often doesn't have a breast lump and may not be detected on a mammogram. It can look like swelling of the breast skin, breast redness, an inverted nipple, or thickening of the breast skin so it looks like orange peel.

Each type of invasive breast cancer has a subtype. Each subtype is based on the characteristics of the cancer cells. This information helps doctors decide which treatments are best suited to kill the cancer cells.

The 4 subtypes of breast cancer are:

This accounts for around two-thirds of breast cancers.⁴ Hormones like oestrogen and/or progesterone cause cancer cells to grow and reproduce. Treatment includes hormone-blocking therapy, usually after other treatments such as chemotherapy or surgery.

Breast cancer cells that are HER2-positive have too much of a protein called human epidermal growth factor receptor 2. Treatments for this sort of breast cancer often include a drug called Trastuzumab alongside surgery, chemotherapy or radiotherapy.

This is a relatively new sub-category that allows doctors to differentiate between HER2-low and HER2-negative cells. There are different amounts of proteins in these 2 cells. This means some drugs work very well on HER2-low cells but not HER2-negative cells. If you have been diagnosed with HER2-negative breast cancer, you may be able to have your tissue re-tested in order to determine if you're eligible for treatment that is suited to HER2-low cells.

Around 15% of breast cancers are triple negative.⁴ This means the breast cancer cells don't contain oestrogen, progesterone or HER2. It's an aggressive form of breast cancer and is usually treated by radiation, surgery, chemotherapy or immunotherapy medications.

Each type of breast cancer is classified in stages. This can be done in stages 1 to 4 or by using the following terms:¹

This refers to invasive breast cancer that is contained within the breast. It may or may not have spread to nearby lymph nodes or the armpit, but if it has, these cells can't yet be detected.

This is an invasive breast cancer that is 5cm or larger or has spread beyond the breast to lymph nodes in the underarm area or tissues around the breast such as skin, muscle or the chest.

Also known as advanced or secondary breast cancer. This means the cancer has spread past the breast to other areas of the body, such as the bones, liver, lungs or brain. It can also spread to other organs.

The Breast Cancer Network Australia offers information and support for those living with breast cancer or those caring for someone with breast cancer.

Cancer Council has information and support online.