Among women breast cancer was the most common cancer (3025 diagnoses) and the third most common cause of death (617 cases) behind lung cancer and colorectal cancer.
Around 30 men are diagnosed with the condition in New Zealand each year which equates to around 1% of all breast cancer diagnoses.
Breasts are composed of fibrous (connective) tissue, fatty tissue and glandular tissue. They lie on a band of strong muscle that sits on the ribs of the chest. Breasts have no useful biological function other than to provide milk for babies.
Fibrous tissue gives the breast its shape and helps to support the fatty tissue and glandular tissue. As women age, the fibrous tissue is replaced with fatty tissue. This leads to changes in the shape and texture of the breasts.
The glandular tissue is made up of a series of lobules. These are small structures that produce milk when stimulated by female hormones during pregnancy. The milk produced in the lobules drains into small channels or ducts that eventually open into the nipple. Glandular tissue also responds to menstrual-related hormonal changes, which can cause the breasts to be occasionally tender and lumpy.
Causes and risk factors
The causes of breast cancer are not known. However, it is known which women are more at risk of developing the condition. The main risk factors for developing breast cancer are:
- Being a woman over the age of 40 years
- Having a family history of breast cancer - the younger the family member was when they developed breast cancer, the greater the risk
- Having had breast cancer previously
- Having had a biopsy showing an "at risk" breast lump or thickening
- Having a faulty gene, such as BRCA1 or BRCA2. Women with a BRCA1 gene mutation have a 55-65% risk of developing breast cancer by age 70 years. For women with a BRCA2 gene mutation the risk is approximately 45%.
Other risk factors include:
- Having had an early onset of periods or the late onset of menopause
- Having had a first child after the age of 30 years or not having had children at all
- A diet high in fat, excessive alcohol and a reduced intake of fibre, fruits and vegetables
- Being on menopausal hormone therapy (formerly known as hormone replacement therapy or HRT) medication for longer than 5-7 years
- Taking the oral contraceptive pill may slightly increase the risk of developing breast cancer, but this has not been conclusively proven
- Having dense breasts - dense breasts do not increase the risk of developing breast cancer, but they may make lumps difficult to feel and see.
Types of breast cancer
Signs and symptoms
Most commonly, the first sign of breast cancer is a new lump in the breast. The lump is usually painless. Other signs of breast cancer include:
- A new area of thickened tissue in the breast
- Nipple discharge or a change in the nipple
- Dimpling or puckering of the skin of the breast
- A change in breast size or shape.
The doctor will begin by examining both breasts. They will then check the abnormal lump's size and location, and other characteristics such as whether it is mobile, hard or soft, regular or irregular. The doctor will ask about the history of the lump such as how long has it been there, has it grown, is it painful. Risk factors such as family history or previous breast lumps will be discussed.
A mammogram (specialised breast x-ray) shows the soft tissue of the breast and can indicate any suspicious areas. Ultrasound scanning uses sound waves to form an image of the breast tissue. Pictures of any suspicious areas can be taken. Ultrasound scanning is particularly useful for assessing whether a lump is fluid filled or solid.
There are different types of biopsies used to take cells or tissue samples from a suspicious lump so they can be sent to a laboratory for analysis under a microscope.
- Fine needle aspiration: This is usually the first type of biopsy used. It is performed using a local anaesthetic and involves inserting a fine needle into the lump and removing a small sample of cells and/or fluid. At the laboratory the sample is spread onto a glass slide and analysed. The insertion of the needle may be guided by ultrasound.
- Core biopsy: This uses a larger needle to remove a sample of tissue from the lump. A local anaesthetic is used and a very small incision (1-2mm) is made in the skin over the lump. The needle is usually guided into the lump by ultrasound. At the laboratory the tissue sample is sliced very finely and placed on a glass slide for analysis.
- Stereotactic core biopsy: This is a core biopsy performed on a special x-ray table allowing three-dimensional computerised images of the lump to be taken and used to guide the biopsy needle into the lump. This is useful for testing lumps seen on a mammogram that cannot be felt or visualised using an ultrasound scanner.
- Excision biopsy: This is a minor surgical procedure where part or all of the abnormal area is removed. It can be performed using a local or general anaesthetic. If the lump is unable to be precisely located using mammogram or ultrasound scanning, it may need to be marked by a thin wire called a "hookwire". This is inserted under x-ray guidance using a local anaesthetic just prior to the surgery.
Stages of breast cancer
In most cases, the breast cancer tumour can be removed without having to remove the entire breast (referred to as breast conserving surgery). The area of the cancer is removed along with a ''margin" of healthy surrounding tissue (usually about 1cm), to ensure that all of the breast cancer is removed.
This operation involves removing the entire breast and all of the breast tissue from just below the collarbone to the upper abdomen. A "simple mastectomy" is when just breast tissue is removed. A "modified radical mastectomy" is when the lymph glands under the arm are also removed.
It is usual practice during breast cancer surgery to remove up to half of the axillary lymph nodes for testing. Testing of the lymph nodes can indicate whether the cancer has spread into the lymphatic system, thus increasing the risk of the cancer spreading to the rest of the body. Axillary node dissection is usually well tolerated but there is a risk that the remaining lymph nodes will not be able to adequately cope with the drainage from the lymphatic vessels in the breast. This can lead to shoulder stiffness, changes in sensation in the area, and a condition known as lymphoedema which is marked by arm swelling.
This type of lymph node biopsy is used in some cases to minimise problems associated with axillary node dissection. During a sentinel node biopsy two special dyes are injected around the breast cancer tumour. One is visible to the naked eye during the biopsy surgery and the other is a weak radioactive substance detectable by either a Gamma camera or a hand-held device like a Geiger counter. The dyes drain through the lymph vessels and into the first node to be involved - the sentinel node. This node is then removed for analysis. If the sentinel node is clear of cancer cells, then it can safely be presumed that the cancer has not spread to the rest of the axillary nodes. If, however, the sentinel node is positive for cancer cells a subsequent procedure to remove the remaining lymph nodes would be needed.
After mastectomy, some women may choose to have the breast reconstructed. This can be done at the time of the mastectomy or at a later date. The surgery is usually performed by a plastic surgeon. The aim of breast reconstruction is to recreate a breast that feels and looks as natural as possible.
This uses radiation to destroy any cancer cells that may be left in the breast. It is most commonly used after lumpectomy/partial mastectomy. However, it may be used after mastectomy if there was more than one tumour, the tumour was large, or the tumour was growing close to the chest wall. A course of radiotherapy is usually given over4-6 weeks, consisting of daily treatments from Monday to Friday. Side effects of the treatment include severe tiredness and burns similar to bad sunburn on the treated area.
This may be given if spread of the cancer is suspected or confirmed and is usually given soon after surgery. Chemotherapy medications can be given by tablet or as injections into the blood stream. Usually it is a combination of both. The medications aim to kill off any cancer cells that may be circulating in the body. There are different strengths and combinations of chemotherapy medications, which are given in cycles. Side effects of chemotherapy treatment may include nausea, hair loss, sores in the mouth and diarrhoea.
For cases where the breast cancer is hormone receptor positive, hormone therapy may be prescribed to help prevent recurrence of the breast cancer. These medications work by blocking the hormone receptors on the breast cancer cells, preventing hormones binding to them and stimulating growth. One common example of this type of medication is tamoxifen. This is commonly given for up to five years after diagnosis of breast cancer. Other types of hormone treatments include anastrozole (Arimidex) or letrozole (Letara).
This type of treatment includes a class of anticancer medications called “monoclonal antibodies”. These medications are formulated to target cancer cells, rather than normal healthy cells. A monoclonal antibody medication used in New Zealand is trastuzumab (Herceptin). This is used to treat women with HER2 positive breast cancer. Trastuzumab works by binding to the HER2 proteins, preventing them from stimulating the cancer cells to grow. It also acts to “flag” the cancer cells to the body, which then stimulates the immune system to destroy the abnormal cells. In New Zealand, trastuzumab is funded for up to 12 months' use in the treatment of women with HER2 positive breast cancer.
It is recommended that all women have screening mammograms from the age of 40 years. Women in high-risk groups may be recommended to start having regular mammograms at an earlier age. Women aged from 45 to 69 years who have had no history of breast abnormalities can have two-yearly mammograms through Breast Screen Aotearoa, a free national screening programme.
It is recommended that women check their breasts regularly. This enables them to learn what their breasts feel like normally so that they are better able to detect any changes or abnormalities in the breast.
Eating a diet low in fat, undertaking regular exercise and limiting alcohol intake may also help to reduce the risk of breast cancer.
Further information and support
This free national mammography service helps check for early breast cancer. The programme is offered to all women in New Zealand aged 45-69 years who have no symptoms.
This organisation is for survivors of breast cancer and their supporters. It aims to promote increased efforts to prevent and cure breast cancer - by advocacy, education, information and networking.
This registered charity offers free workshops teaching techniques to restore appearance and self-image to women coping with the side effects of cancer treatment. Group workshops are held nationwide.
Provides support and information for women with metastatic breast cancer.
Cancer Society of New Zealand (2012). A Guide for women with breast cancer (Information Sheet). Wellington: Cancer Society NZ. https://auckland-northland.cancernz.org.nz/assets/Cancer-information-2/IS-Guide4WomenwithBreastCancer-13Feb2012.pdf
Ministry of Health (2012). Cancer: New registrations and deaths 2012 (Web Page). Wellington: Ministry of Health. http://www.health.govt.nz/publication/cancer-new-registrations-and-deaths-2012 [Accessed: 18/10/16]
National Cancer Institute (2015). BRCA1 and BRCA2: Cancer risk and genetic testing (Web Page). Bethesda, MD: National Cancer Institute at the National Institutes of Health. https://www.cancer.gov/about-cancer/causes-prevention/genetics/brca-fact-sheet [Accessed: 18/10/16]
The New Zealand Breast Cancer Foundation (2013). Risk factors (Web Page). Auckland: New Zealand Breast Cancer Foundation. http://www.nzbcf.org.nz/BREASTCANCER/RiskFactors.aspx [Accessed: 18/10/16]
The New Zealand Breast Cancer Foundation (2013). Breast cancer in NZ (Web Page). Auckland: New Zealand Breast Cancer Foundation. http://www.nzbcf.org.nz/BREASTCANCER/Overview/BreastCancerinNZ.aspx [Accessed: 18/10/16]
Last Reviewed – October 2016