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Breast cancer starts in the cells of the breast. A cancerous (malignant) tumour is a group of cancer cells that can grow into and destroy nearby tissue. It can also spread (metastasize) to other parts of the body.
Cells in the breast sometimes change and no longer grow or behave normally. These changes may lead to non-cancerous (benign) breast conditions such as atypical hyperplasia and cysts. They can also lead to non-cancerous tumours such as intraductal papillomas.
But in some cases, changes to breast cells can cause breast cancer. Most often, breast cancer starts in cells that line the ducts, which are the tubes that carry milk from the glands to the nipple. This type of breast cancer is called ductal carcinoma. Cancer can also start in the cells of the lobules, which are the groups of glands that make milk. This type of cancer is called lobular carcinoma. Both ductal carcinoma and lobular carcinoma can be in situ, which means that the cancer is still where it started and has not grown into surrounding tissues. They can also be invasive, which means they have grown into surrounding tissues.
Less common types of breast cancer can also develop. These include inflammatory breast cancer, Paget disease of the breast and triple negative breast cancer. Rare types of breast cancer include non-Hodgkin lymphoma and soft tissue sarcoma.
Breast cancer is the most common cancer among Canadian women (excluding non-melanoma skin cancers). It is the 2nd leading cause of death from cancer in Canadian women. Breast cancer can also occur in men, but it is not common.
In 2017, an estimated:
- 26,300 women were diagnosed with breast cancer. This represents 25% of all new cancer cases in women in 2017.
- 5,000 women died from breast cancer. This represents 13% of all cancer deaths in women in 2017.
- On average, 72 Canadian women were diagnosed with breast cancer every day.
- On average, 14 Canadian women died from breast cancer every day.
- 230 men were diagnosed with breast cancer and 60 died from breast cancer.
- Personal history of breast cancer
- Family history of breast and other cancers - Having one first-degree relative with breast cancer approximately doubles a woman’s risk. The more first-degree relatives with breast cancer, the greater the risk. The risk with second-degree relatives is not as much as the risk with first-degree relatives.
- BRCA gene mutations - BRCA1 (breast cancer gene 1) and BRCA2 (breast cancer gene 2) are normally found in the body. They are called tumour suppressor genes because they appear to play a role in controlling the growth of cancer cells. Mutations in the BRCA1 or BRCA2 genes can affect them so they no longer control cancer growth. These mutations are rare. They occur in about 1 in 500 people. Studies show that women with inherited BRCA1 or BRCA2 gene mutations have up to an 85% chance of developing breast cancer in their lifetime. Women with these inherited mutations also have a higher risk of developing breast cancer at a younger age (usually before menopause) than other women. Women with a BRCA gene mutation also have a higher risk of developing cancer in both breasts. If they develop cancer in one breast, they have a greater risk of developing cancer in the other breast. Having BRCA gene mutations also increases a woman’s risk of developing ovarian cancer at any age.
- Certain genetic conditions - Li-Fraumeni syndrome, Ataxia telangiectasia , Cowden syndrome, Peutz-Jeghers syndrome
- Other gene mutations –
- CHEK2 gene mutation has been identified in some families with Li-Fraumeni syndrome. It is normally a tumour suppressor gene. When it is mutated, it increases breast cancer risk.
- PALB2 gene mutation means that it loses its function. It normally protects against breast cancer by helping repair changes to DNA and preventing tumour growth. When this gene loses its function, there is a higher risk for breast cancer.
- Ashkenazi Jewish ancestry
- Dense breasts
- Reproductive history - Starting your period early means that your cells are exposed to estrogen and other hormones for a greater amount of time. This increases the risk of breast cancer. If you enter menopause at a later age (after age 55), it means that your cells are exposed to estrogen and other hormones for a greater amount of time. This increases the risk for breast cancer. Women who have their first full-term pregnancy after the age of 30 have a slightly higher risk of breast cancer than women who have at least one full-term pregnancy at an earlier age. Becoming pregnant at an early age (such as before age 20) reduces breast cancer risk. The more children a woman has, the greater the protection against breast cancer. Not becoming pregnant at all (called nulliparity) increases the risk for breast cancer.
- Exposure to ionizing radiation - Women who have received radiation therapy to the chest, neck and armpit area (called the mantle radiation field) have a higher risk of developing breast cancer.
- Hormone replacement therapy
- Oral contraceptives
- Atypical hyperplasia
- Alcohol - Even low levels of alcohol consumption (just over one drink per day) can increase a woman’s risk. The risk increases with the amount of alcohol consumed.
- Being obese - Studies show that women who have never taken hormone replacement therapy and who have a body mass index (BMI) of 31.1 or higher have a 2.5 times greater risk of developing breast cancer than those with a BMI of 22.6 or lower.
- Physical inactivity
- High socio-economic status
- Tall adult height
What is a mammogram?
Mammograms are x-rays of the breasts. A screening mammogram looks for an unsuspected, hidden cancer in women who are healthy and who have never had breast cancer.
Who should get a mammogram?
The Canadian Association of Radiologists (CAR), National Standards and Guidelines for Breast Screening, recommend mammography screening for asymptomatic women at least 40 years of age. If you meet the following criteria you should call and book an appointment to have a mammogram (you are not required to have a referral by a physician).
- Minimum age 40
- No new breast symptoms
- No breast implants
- No personal history of breast cancer
- Minimum one year since previous mammogram
- Resident of Nova Scotia with a valid Nova Scotia Health card
How often should you have a mammogram?
Women in Nova Scotia, aged 40-49, are recommended to have annual screening mammography
Women in Nova Scotia, aged 50-69, are recommended to have screening mammography at two year intervals. Women 50-69 can also be recommended to return on an annual basis if they:
Women over the age of 70 are recommended to continue to have screening mammography if they are in good health.
If you notice any of these signs, you should see your doctor for a breast examination. Your doctor may then refer you for a mammogram.
- A mass or a lump or a thickening or a change in your breast that is new or stays over time. 80% - 90% of breast lumps are not cancer.
- A lump in your breast increases in the size, or your entire breast changes in size (gets visibly smaller or larger). Painful lumps are less likely to be cancer.
- Your nipple begins to draw in.
- There is dimpling or puckering of the skin of the breast.
- There is a change in the contour (shape) of your breast.
- You have bloody or watery nipple discharge.
- Redness, scaling or inflammation of the nipple.
- Your breast becomes red, swollen or hot.
- A lump under your arm / in your armpit
Websites to visit for more information:
Canadian Cancer Society: http://www.cancer.ca/en/cancer-information/cancer-type/breast/breast-cancer/?region=on
Nova Scotia Breast Screening Program: https://breastscreening.nshealth.ca/breast-imaging-guidelines