What should I know about breast cancer?

Breast cancer is the most common cancer in Canadian women. It can also be found in men but this is very rare. Almost all breast cancers start in the glandular tissue of the breast and are known as adenocarcinomas. Cancer cells may start within the ducts (ductal carcinoma) or lobules (lobular carcinoma). Ductal carcinoma is the most common type of breast cancer.

What causes breast cancer?

There is no single cause of breast cancer but some factors that increase the risk of developing the disease include:

• Age: 80% of the cases of breast cancer occur in women over 50 years of age.
• Family history of breast cancer, especially in a mother, sister or daughter diagnosed before menopause, or if a mutation on the BRCA1 or BRCA2 genes is present.
• Previous breast disorders with biopsies showing abnormal cells.
• No full term pregnancies or having a full term first pregnancy after age 30.
• High breast tissue density.
• In post menopausal women: obesity and physical inactivity.
• Beginning to menstruate at an early age.
• Later than average menopause.
• Taking hormone replacement therapy (estrogen plus progestin) for more than 5 years.
• The use of oral contraceptives, may be associated with a slight increase in breast cancer risk.
• Alcohol use is associated with a modest increase in breast cancer risk.

Early detection and screening for breast cancer

Detecting and treating breast cancer early is very important. While breast self-examination (BSE) helps you learn what is normal for your breasts so that you will notice changes, mammography and clinical breast examinations are the most reliable methods of detecting breast cancer.

The Canadian Cancer Society recommends the following guidelines:

• If you are between the ages of 40 and 49, there may be some benefit from regular mammography, but the science is inconclusive. Research does suggest that if women in their 40s choose to have a mammogram, they should consider having one every year because breast cancers may act differently in younger women.
• Have a mammogram every 2 years if you are between the ages of 50 and 69.
• If you are over 70, talk to your doctor about a screening program for you.
• Have a clinical breast examination by a trained health professional at every 2 years if you are over the age of 40.
• Consider doing breast self-examination (BSE). Being aware of your breast tissue may help you to notice changes in your breasts that can be reported to your doctor.

Additional resources

• Canadian Partnership Against Cancer
• Canadian Breast Cancer Research Alliance
• Canadian Cancer Society
• Canadian Breast Cancer Network
• Breast Cancer Society of Canada
• Cure Foundation
• Canadian Task Force on Preventive Health Care
• Cancer Care Ontario
• National Cancer Institute
• National Institutes of Health
• Centers for Disease Control and Prevention
• International Agency for Research on Cancer
• The Cochrane Collaboration
• Willow Breast Cancer Support Canada
• Breast Cancer Society of Canada
• National Cancer Institute: Surveillance, Epidemiology, and End Results (SEER)
• Cancer Research UK

Prepared by the Canadian Cancer Society. This information appeared originally on the Canadian Health Network Web site.