Types of breast cancer

Breast cancer is a term that describes a range of diseases affecting the breast tissue. There are different types and subtypes of disease that are referred to as breast cancer. Each may require a different type of treatment, which is why the treatment you receive for your breast cancer may be quite different from the treatment other people may have.   

The types of breast cancer include non-invasive and invasive breast cancers. Non-invasive breast cancer include ductal carcinoma in situ (DCIS) and lobular carcinoma in situ (LCIS). It is important to note that some clinician groups refer to DCIS and LCIS as non-invasive breast cancers, while others refer to DCIS and LCIS as conditions and/or abnormal breast cell changes. BCNA supports all people affected by DCIS or LCIS.

Invasive ductal carcinoma and invasive lobular carcinoma are the most common types of invasive breast cancers. Less common types of breast cancer include Paget’s disease, phyllodes tumours, inflammatory breast cancers and other rare cancers. 

Breast cancers are further classified according to subtype and stage. The subtypes of breast cancer (e.g. hormone receptor-positive breast cancer, HER2-positive breast cancer, triple negative breast cancer)  are based on the receptors on its cells. Additionally, the staging of breast cancer (I to IV, or 1 to 4) incorporates information about the size of the cancer and how far it has spread.  

You will find more information about the types, subtypes and stages of breast cancer in the information provided below. 

Non-invasive breast cancers 

Non-invasive breast cancers are abnormal cells that are contained within the milk ducts or lobules in the breast. They have not grown into or invaded normal breast tissue. Non-invasive cancers are called “carcinoma in situ” and are sometimes referred to as “pre-cancers”.  

Ductal carcinoma in situ 

Ductal carcinoma in situ (DCIS) is the most common type of non-invasive breast cancer. DCIS is the name for abnormal changes in cells in the milk ducts of the breast. It is non-invasive because it hasn't spread into any surrounding breast tissue. For this reason, DCIS isn't considered to be invasive cancer. DCIS isn't life-threatening, but having DCIS can increase the risk of developing an invasive breast cancer later in life.  Your doctor will talk to you about treatment followed by regular, long-term follow-up which may include more frequent clinical examinations and screening. 

Lobular carcinoma in situ 

Lobular carcinoma in situ (LCIS) is where abnormal cells have formed in the lobules (the milk-producing glands at the end of breast ducts). It is non-invasive as it has not spread into any surrounding breast tissue. Despite its name, LCIS is considered a benign breast change and not a breast cancer. Having LCIS may increase the risk of developing invasive breast cancer later in life. Your doctor will talk to you about regular long-term follow-up, which may include more frequent clinical examinations and screening.

Invasive breast cancers 

Invasive breast cancers have spread outside the ducts or lobules of the breast into surrounding breast tissue.  

Invasive ductal carcinoma

Invasive ductal carcinoma (IDC) is the most common type of (invasive) breast cancer. About 80% of all breast cancers are invasive ductal carcinomas. Invasive ductal carcinoma means that the cancer that began in the milk ducts of the breast has broken through the lining of the milk duct and spread into the surrounding breast tissue. Over time invasive ductal breast cancer can spread to the lymph nodes and potentially to other parts of the body.  

Invasive lobular carcinoma

Invasive lobular carcinoma (ILC) is the second most common type of breast cancer after invasive ductal carcinoma. Invasive lobular carcinoma is cancer that begins in the milk-producing lobules of the breast, breaks through the lining of the lobule and spreads into surrounding breast tissue. Over time invasive lobular breast cancer can spread to the lymph nodes and potentially to other parts of the body.  

Subtypes of breast cancer  

There are four main subtypes (biomarkers) of breast cancer that are based on the receptors a cancer expresses, which control how the cells behave. This information helps guide doctors about which treatments are best targeted to kill the cancer cells. It also helps doctors understand prognosis. Research in the genetic makeup of breast cancer is continuing to help improve treatments to target specific aspects of the cancer cells. This is leading to more personalised treatment for breast cancer. 

The main pathologic subtypes of breast cancer are:  

Hormone receptor-positive breast cancer 

About two-thirds of breast cancers are hormone receptor-positive, which means that female hormones (oestrogen and/or progesterone) cause them to grow and reproduce. Most people with hormone positive breast cancer will be offered hormone-blocking therapy such as tamoxifen, anastrozole or letrozole. These are oral (tablet) medications that are taken daily for five years or more following the completion of other breast cancer treatments (surgery, chemotherapy and/or radiotherapy).  

HER2-positive breast cancer 

HER2-positive breast cancer cells have too much of the protein called human epidermal growth factor receptor 2 (HER2) on the surface of the cancer cells compared with normal cells. These excess HER2 receptors promote the growth of the cancer cells. HER2-positive breast cancer may be either hormone receptor positive or negative. Around 20% of breast cancers are HER2 positive.  

There are a number of effective targeted therapies to treat HER2-positive breast cancers. The targeted therapies are designed to target specific characteristics of the cancer cells such as the HER2 protein, stopping the cancer cells from dividing and growing, and helping to kill the cancerous cells. The drug trastuzumab is the most common targeted therapy for HER2-positive breast cancer. Most people with HER2-positive breast cancer will have targeted therapies along with other treatments including surgery, chemotherapy and/or radiotherapy. They may also be recommended hormone-blocking therapy if the cancer is also hormone receptor-positive. 

HER2-low breast cancer

HER2-low breast cancer is a new sub-category of breast cancer. The difference between HER2-positive, HER2-negative and HER2-low is the number of HER2 proteins in the cancer cell.

Until 2023, breast cancers with a low number of HER2 proteins in the cancer cells were classified as ‘HER2-negative’. People with HER2-negative breast cancer were not eligible for anti-HER2 targeted therapy because in trials these tumours did not respond to HER2 targeted therapies.

However, the new subcategory of HER2-low was created after clinical trials showed some drugs work really well on cancers that have lower amounts of HER2.

If you have previously been told your breast cancer is HER2-negative, talk to your treating team. They may suggest you have the tissue retested to find out if you are eligible for anti-HER2 therapies such as Enhertu.

Triple negative breast cancer 

Triple negative breast cancer does not have any of the three receptors commonly found on breast cancer cells (oestrogen, progesterone and HER2). Around 15 per cent of breast cancers are triple negative and treatment such as radiation, surgery and chemotherapy is generally recommended for these cancers. Triple negative is an aggressive form of breast cancer. Targeted therapies and the role of immunotherapies are being actively studied in the treatment of triple negative breast cancers. Immunotherapy medicines work by helping the immune system work harder and better to fight cancer cells. 

Breast cancer stages 

Early breast cancer

“Early breast cancer” is the term that refers to invasive breast cancer that is contained within the breast that may or may not have spread to nearby lymph nodes in the breast or armpit (axilla) but not anywhere else in the body. Breast cancer stages 1 and 2 are examples of early breast cancer. For more information about breast cancer stages, read Breast cancer stage in My Journey.

Locally advanced breast cancer 

Locally advanced breast cancer (stage 3) is an invasive breast cancer that is 5cm or larger or has spread beyond the breast to other nearby areas such as the skin, chest wall or muscle and may have extensive local lymph node involvement. 

Metastatic breast cancer 

Metastatic breast cancer – also known as advanced, secondary or stage 4 breast cancer – is breast cancer that has spread to more distant parts of the body such as the bones, liver, lungs or brain although it has the potential to spread anywhere in the body.

Less common types of breast cancer  

Paget's disease of the nipple

Paget's disease of the nipple is a rare form of breast cancer in which cancer cells grow in the nipple or the areola (the area around the nipple). The nipple and areola often become scaly, red, itchy and irritated. Many people with Paget’s disease may also have either DCIS or invasive breast cancer somewhere else in the breast. The unusual changes in the nipple and areola are often the first signs that breast cancer is present.  

Phyllodes tumours of the breast

Phyllodes tumours of the breast are rare. Although most phyllodes tumours are benign (not cancerous), some are malignant (cancerous). Phyllodes tumours tend to grow quickly, but they rarely spread outside the breast. Phyllodes tumours develop in the breast’s connective tissue or stroma (the tissue that holds everything together inside the breast), i.e. outside the ducts and lobules of the breast.  

Inflammatory breast cancer

Inflammatory breast cancer is a rare and aggressive form of breast cancer. It doesn't look like a typical breast cancer and often does not cause a breast lump. In inflammatory breast cancer the cancer cells often block the small lymph vessels in the skin of the breast. When the lymph vessels become blocked, it causes the skin to become red, swollen and inflamed, like an infection. 

Other rare breast cancers

There are also other types of very rare breast cancers such as metaplastic, medullary and mucinous breast cancer. These types of breast cancers have cells with special features, often named based on how the cells look under the microscope.