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BREAST CANCER TYPES

Learn more about the different types of breast cancer.

Breast cancer is not just one disease, but several. The type of breast cancer being diagnosed is determined by the specific cells in the breast that are affected. Breast cancer can begin in different areas of the breast – the ducts, the lobules or in some rarer cases, the tissue in between.

Each patient will receive their own treatment plan based on their breast cancer type, subtype, and stage of disease. Advances in treatment has allowed for each treatment plan to be more personalised for patients, which results in better treatment and outcomes. Therefore, your treatment may be different from other breast cancer patients.

Breast cancer can be broken down into two main categories: invasive or non-invasive.

What is Non-Invasive Breast Disease (or Tumour)?

Non-invasive breast cancer is cancer which is contained within the milk ducts or lobules in the breast. It is cancer which has not grown into the normal breast tissue.

Non-invasive breast cancer is sometimes called carcinoma in situ, which means ‘in the same place’, or pre-cancers. Non-invasive breast cancer can either be ductal carcinoma in situ or lobular carcinoma in situ.

Ductal Carcinoma in Situ

Ductal carcinoma in situ, or DCIS, is a non-invasive breast condition which affects around 1,200 women per year in Australia. DCIS is the name for abnormal changes in the cells located in the milk ducts of the breast.

These abnormal changes have the potential to turn into invasive cancer cells, however DCIS is not considered invasive in itself. In DCIS, the abnormal cells are contained within the milk ducts and cannot travel to other parts of the body.

DCIS cannot usually be felt as a lump, but is typically found on a mammogram or ultrasound. Without treatment, some people (but not all) with DCIS develop invasive breast cancer. Treatment of DCIS usually involves breast surgery and in certain cases radiotherapy. Occasionally surgery to remove lymph nodes and/or hormonal therapies are used.

Lobular Carcinoma in Situ

Lobular carcinoma in situ or LCIS is a non-invasive breast condition. LCIS is the name for abnormal cells that are contained to the lobules (milk glands) and ducts of the breast.

Like DCIS, these abnormal changes can turn into invasive cancer cells, but it is not breast cancer as we more commonly understand it. A woman cannot die from LCIS as the cells are contained within the milk producing structures of of the breast.

LCIS cannot usually be felt but is generally found in a mammogram or when a biopsy is taken for another reason. LCIS does not require treatment if there are no other abnormal changes to the breast. However, a woman with LCIS should be carefully monitored as having LCIS increases the chance of developing breast cancer in future.

What is Invasive Breast Cancer?

Invasive breast cancer means that the cancer has spread from the original site to other areas, like neighbouring breast tissue, lymph nodes or elsewhere in the body. The two main invasive breast cancers are invasive ductal carcinoma and invasive lobular carcinoma.

Invasive Ductal Carcinoma

Invasive ductal carcinoma is a broad term used to classify cancer that began growing in a milk duct and has invaded the fibrous or fatty tissue of the breast outside the duct. Invasive ductal carcinoma accounts for around 80 per cent of all breast cancers diagnosed.

Invasive Lobular Carcinoma

Invasive lobular carcinoma, the other major histological subtype, is a breast cancer that has spread beyond the lobules and ducts, potentially spreading to the lymph nodes and other parts of the body. Typically, invasive lobular carcinoma tumours are associated with a good prognosis, being intermediate grade and oestrogen receptor positive. However, the tumour can sometimes lead to metastases.

Paget’s Disease of the Nipple

Paget’s disease of the nipple is a rare form of breast cancer that affects the nipple and the area around the nipple (the areola). It is commonly associated with an invasive cancer elsewhere in the breast. Around two of every 100 cases of breast cancer involve Paget’s disease of the nipple. The main sign of Paget’s disease of the nipple is a change in the nipple and/or areola. Treatment can include breast surgery and radiotherapy.

Inflammatory Breast Cancer

Inflammatory breast cancer is a rare form of breast cancer that affects the lymphatic vessels in the skin of the breast. This type of breast cancer does not present as a lump but rather a redness or rash in appearance, as a result of the lymphatic vessels becoming blocked, and the breast becoming red and swollen, similar to an infection. Most women with inflammatory breast cancer will have a combination of treatments that can include surgery, chemotherapy, radiotherapy, hormonal therapies, and targeted therapies.

Breast Cancer Subtypes

Breast cancer can be divided into four different molecular subtypes: Luminal A, Luminal B, Triple Negative or HER2 positive. These are defined by the proteins involved, or not involved, in each cancer diagnosis.

Hormone Receptor Positive HER2 Negative (HR+/HER2-) or Luminal A Breast Cancer

This is the most common subtype of breast cancer. Luminal A tumours grow at a slower rate than other cancer types, which means they have a better prognosis. This subtype is positive for oestrogen receptor and/or progesterone receptor and negative for HER2, which stands for human epidermal growth factor receptor 2.

As Luminal A cancers are HR positive, patients who undergo breast surgery may receive hormonal treatments to block hormones from fueling cancer growth.

Hormone Receptor Positive HER2 Negative (HR+/HER2+) or Luminal B Breast Cancer

Luminal B breast cancers are positive for oestrogen receptor and/or progesterone receptor and may have either normal or higher than normal about of HER2. Luminal B cancers tend to grow faster than the Luminal A type.

Luminal B cancers are more often treated with chemotherapies and HER2 targeted therapies compared with Luminal A cancers.

HER2 Positive Breast Cancer

HER2 positive breast cancer is any type of breast cancer that tests positive for a protein called human epidermal growth factor receptor 2 (HER2). HER2 positive breast cancer is a faster growing form of breast cancer compared with HER2 negative disease, but is also highly treatable.

HER2 positive breast cancer is treated using HER2 targeted therapy. The most common HER2 targeted therapy available in Australia and New Zealand is trastuzumab (Herceptin). Herceptin was found to significantly reduce breast cancer returning, as reported in the Breast Cancer Trials HERA Clinical Trial.

For women with HER2 positive metastatic breast cancer, anti-HER2 therapies may be given on their own or with other treatments and will continue so long as the benefit to the patient outweighs the side effects.

Triple Negative Breast Cancer

Triple negative breast cancer is breast cancer that tests negative for all three major growth receptors – oestrogen, progesterone and HER2. Triple negative breast cancer is typically a faster-growing cancer that occurs at an earlier age on average. It has a greater chance of developing into a metastatic stage and has poorer clinical outcomes as shown by higher relapse rates and lower survival rates, compared with other breast cancer subtypes diagnosed at the same stage. It is important to note, however, that many patients with early-stage triple-negative breast cancer are cured – especially if the cancer is diagnosed early.

Standard treatment of triple negative breast cancer typically consists of surgery, chemotherapy and usually a course of radiotherapy. Often chemotherapy treatment is given prior to breast surgery (neoadjuvant chemotherapy) as it is effective in reducing the size of breast cancer while providing useful information about the effectiveness of the treatment being given.

How Common is Breast Cancer?

Breast Cancer today inAustralia and New Zealand

Breast Cancer today In Australia

In Australia, the risk of a woman being diagnosed with breast cancer by the age of 85 is

1 IN 7

.. for men 1 in 670

… and New Zealand

In New Zealand, the risk of a woman being diagnosed with breast cancer in their lifetime is

1 IN 9

Breast Cancer Risk Factors

A risk factor is something about a person, or what that person is exposed to, that increases their ‘risk’ (in other words, the chance or likelihood) of developing breast cancer in future. This might be something about their genetic makeup that cannot be changed, or a lifestyle factor like alcohol of lack of exercise. But risk factors don’t tell us everything. Having a risk factor, or even several risk factors, does not mean a woman will definitely be diagnosed with breast cancer and many who are diagnosed do not have any known risk factors.

There is currently no way to definitively prevent breast cancer. However, you can assess your risk factors and their impact on your cancer risk using the iPrevent tool. Some risk factors can be modified, others cannot, and these may include:

  • Age

    The risk of breast cancer increases with age, with about 79% of all new breast cancer diagnosed in women aged 50 and over. The average age of first breast cancer diagnosis in Australia is 61 years.

    Besides gender, aging is the most significant risk factor associated with breast cancer [4]. The older you get, the more your cells accumulate DNA damage (mutations) and are therefore more likely to progress to cancer. According to Cancer Australia, women who are 50 years old are approximately 10 times more likely to develop breast cancer compared to women who are 30 years old.

  • Alcohol

    Alcohol consumption is associated with an approximate 30-50% increased risk in breast cancer risk [1]. Alcohol consumption is the most-established dietary risk factor of breast cancer thought to be due to the increase of endogenous oestrogen levels it causes [2]. 

    Your relative risk of breast cancer is increased by 7% of each additional 10 grams, or one standard drink, of alcohol consumed per day [3]. One standard drink is equivalent to 100mL of wine, 285mL full strength beer, 425mL low strength beer or 30mL (one nip) of spirits.

    Evidence shows there is no safe level of alcohol consumption in regard to breast cancer risk. A large meta-analysis of 222 articles finding even light drinking (up to one drink per day) increases the risk of breast cancer in women. The risk increases further with each extra drink.

  • Family History

    A family history of breast cancer means having one or more blood relatives who have received a breast cancer diagnosis.

    Studies have found that women with one first-degree relative with breast cancer have almost two times the risk of developing breast cancer compared to a woman without any affected relatives. Furthermore, this becomes a three times higher risk for women with two or more first-degree relatives with breast cancer [5]

    Approximately 5-10% of breast cancers are due to a strong family history (two or more close relatives) of genetic mutation such as BRCA1 or BRCA2. There are also lesser known gene-mutations linked to a higher breast cancer risk such as TP53, PTEN, CDH1 and STK11 and some rare moderate-risk gene mutations such as PALB2, ATM and CHEK2. Some women with strong family histories receive genetic testing to see if they have one of these mutations. You can learn more about genetic testing in this Breast Cancer Trials podcast.

    You can learn more about the genetic risks for developing breast cancer here.

    Breast Cancer Trials currently has a breast cancer prevention trial for those with the BRCA1 gene mutation. You can learn more here.

  • Dense Breasts

    Even though breast density is a lower risk than other risk factors such as family history, it is more common in the general population [6]. Mammographic density, or dense breasts, refers to the percentage of dense tissue of an entire breast and can be seen as the whiteness on your mammogram. Breast density cannot be felt or touched and can only be determined through x ray or mammograms.

    Women with dense breasts face two challenges; a potential late diagnosis of breast cancer due to poor sensitivity of mammographic screening and having a higher risk for developing breast cancer [7]. Researchers are uncertain as to why having dense breasts increases your breast cancer risks, but believe it has some genetic links. It is hypothesized that the greater proportion of epithelial and non-epithelial cells in areas of high breast density, and the greater cumulative exposure to hormones and growth factors, may stimulate more cell division which increases breast cancer risk [8].

    Breast density is just one risk factor and doesn’t mean you will be diagnosed with breast cancer. However, if you are aware of your mammographic density, you should talk with your doctor about regular screening. You can learn more about dense breasts in this podcast.

  • Being Overweight

    Being overweight or obese is a known breast cancer risk factor. Obesity is associated with a 20% to 40% increased risk of breast cancer in post-menopausal women. In patients diagnosed with breast cancer, obesity is associated with a 33% increased risk of cancer recurrence and of death from any cause [9].

    Additionally, gaining weight as an adult is associated with an increased risk of post-menopausal breast cancer. The risk increases by about 6% for each 5 kg increase in a woman’s weight.

    However, having a higher BMI before menopause is associated with a decreased risk of premenopausal breast cancer. For each 5-unit increase in BMI, the risk of premenopausal breast cancer is decreased by about 7% [10]. Importantly, obesity throughout life increases the risk of many other diseases such as heart disease and other cancers, leading to a higher rate of premature death.

    You should aim to lead an active life-style, with the Australian Government guidelines recommending 150 to 300 minutes (2 ½ to 5 hours) of moderate intensity physical activity or 75 to 150 minutes (1 ¼ to 2 ½ hours) of vigorous intensity physical activity, or an equivalent combination of both moderate and vigorous activities, each week if aged between 18-64. For those aged 65 and older, the recommendation is to be physically active for 30 minutes every day. This should be balanced with a healthy diet full of nutritious wholefoods [11].

  • Previous Radiation

    Previous exposure to radiation is a known breast cancer risk factor, which increased according to how much radiation you have been exposed to and when you were exposed. Age is an important factor, with females exposed before age 20 years having the highest risk and minimal risk for those exposed to radiation after menopause [12].

    Usually, this exposure to radiation therapy for young people in the chest region is due to treatment for Hodgkin lymphoma or childhood cancers. Women who were treated for hodgkin lymphoma using radiation alone have about five times the risk of breast cancer as women who did not receive this treatment. The risk is higher for those treated at a younger age, particularly close to the age when periods started [13].

  • Smoking

    Researchers have found an increased risk of breast cancer for those who smoke, particularly among women who started smoking at adolescence or younger ages. The relative risk of breast cancer associated with smoking has been found to be greater for women with a family history of the disease [14]

    The carcinogenic potential of tobacco smoke is unarguable and has been definitively linked to heart disease, lung cancer and many other cancers, therefore not smoking is the best choice for your health.

It’s important to know your personal breast cancer risk and manage any risks that can be changed, such as smoking, diet and exercise. Regular screening is important for those in the targeted age group of 50 – 74. If you are younger and concerned about your breast cancer risk, speak with your GP about your screening options.

Breast Cancer Signs and Symptoms

In the early stages of breast cancer there may be no symptoms at all. As the cancer grows, symptoms can include:

  • A new lump in the breast, armpit area or around the collarbone.
  • A change in breast size or shape.
  • Changes to the nipple, such as sores or crusting, an ulcer or inverted nipple.
  • Clear or bloody nipple discharge.
  • Changes to the skin including redness, puckering or dimpling (an ‘orange peel’ appearance).
  • Breast tenderness or pain.

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