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Breast cancer

Understanding the Anatomy of the Breast to Better Understand Breast cancer

breast anatomy

The breast is made of fat, connective tissue, glands and ducts and includes:

  • Ligaments (dense bands of connective tissue that support the breast and run from the skin through the breast and attach to muscles on the chest)
  • Lobules (groups of glands that make milk - there are 15–25 lobules in each breast)
  • Ducts (tubes that carry milk from the lobules to the nipple)
  • Nipple (located in the centre of the areola, composed of muscle fibres)
  • Areola (round, pinkish or brownish area around the nipple)

Breast’s Lymphatic System

The breast contains many blood and lymphatic vessels. Lymphatic vessels are thin tubes that collect and transport the lymph away from the breast to small masses of bean-shaped lymphatic tissue called lymph nodes, which surround the mammary region.

The vessels and lymph nodes are part of the lymphatic system, which helps fight infections. There are several groups of lymph nodes that drain each breast. They are found on both sides of the body:

  • Supraclavicular lymph nodes (above the collarbone)
  • Infraclavicular, or subclavicular, lymph nodes (below the collarbone)
  • Internal mammary lymph nodes (inside the chest around the sternum).

The axillary lymph nodes are under the arm (called the axilla). They are divided into 3 levels based on how close they are to the large muscle of the chest (called the pectoralis major). When breast cancer spreads, it usually spreads to level I lymph nodes, then to level II and then to level III:

  • Level I, or low axilla, are along the outer border of the muscle under the pectoralis major (called the pectoralis minor)
  • Level II, or mid axilla, are beneath the pectoralis minor
  • Level III, or high axilla, are along the inner border of the pectoralis minor

Signs and Symptoms

The most classic sign of breast cancer is a bump or swelling in a breast that does not cause pain. Other possible signs of breast cancer may include:

  • Change in breast size or shape
  • Increased redness, swelling or heat in a breast
  • Mass in the armpit
  • Inverted nipple, i.e., turned inward
  • Abnormal nipple discharge

Types of Breast Cancer

Breast cells sometimes experience changes that make their growth pattern or behaviour abnormal. These changes can lead to non-cancerous (benign) breast conditions, such as atypical hyperplasia and cysts. They can also lead to the formation of non-cancerous tumours, including intraductal papillomas.

However, in some cases, these breast cell changes can cause breast cancer. Breast cancer occurs most often in the cells lining the ducts, which are tubes that transport milk from the glands to the nipple. This type of breast cancer is called ductal carcinoma.

Cancer can also form in lobule cells, which are groups of milk-producing glands. This type of cancer is called lobular carcinoma. Ductal carcinoma and lobular carcinoma can be in situ, meaning that the cancer remains in its original location and has not spread to neighbouring tissues. They can also be infiltrating, or invasive, meaning they have spread to neighbouring tissues.

Some less common types of breast cancer may also occur. Examples include inflammatory breast cancer, Paget disease and triple negative breast cancer. Rare types of breast cancer include non-Hodgkin’s lymphoma and soft tissue sarcoma.

Ductal Carcinoma and Lobular Carcinoma

Almost all breast cancers are adenocarcinomas. These tumours start in gland cells. The most common breast adenocarcinomas are ductal carcinoma and lobular carcinoma.

Physicians categorize these tumours as “non-invasive” or “invasive”. Non-invasive means that the cancer cells have not spread beyond the duct or gland where they started. Invasive means that the cancer cells have started to spread into the surrounding tissue.

Ductal Carcinoma

Ductal carcinoma starts in gland cells in the breast ducts and is the most common type of breast cancer.

Lobular Carcinoma In Situ (LCIS)

LCIS is a buildup of abnormal cells in the lobules that do not spread outside the lobules into nearby breast tissue.

LCIS is most often found when a biopsy is done to check a breast lump or to follow up on an abnormal mammography.

LCIS is neither a true precancerous condition nor breast cancer. It is a sign, or marker, that a woman is at a higher risk of developing breast cancer in the future. Many women with LCIS do not develop invasive breast cancer.

Invasive Lobular Carcinoma

This type of cancer accounts for about 10% of all invasive breast cancers. It starts in the lobules, and then grows through the lobules and into nearby breast tissue. It can also spread (metastasize) to lymph nodes and other parts of the body and it can occur in more than one area of the breast (called multifocal, or multicentric disease).

Invasive lobular carcinoma cells don’t make a lump. They grow in a single strand into the fatty tissues of the breast and make a thickened area of breast tissue. It is difficult to diagnose infiltrating lobular carcinoma by mammogram (biopsy, ultrasound or MRI are most often used).

Inflammatory Breast Cancer

Inflammatory breast cancer develops when cancer cells block the lymph vessels in the skin of the breast. It is called inflammatory because the breast becomes red and swollen. It more often affects young women and women of African descent and is rare and aggressive. In most cases, it has already spread to the lymph nodes or other organs at the time of diagnosis.

Paget Disease of the Breast

Paget disease of the breast is a rare type of breast cancer that develops as a rash or other skin changes on the nipple, usually on only one breast. Paget disease of the breast is more common in women over the age of 50.

Most women with Paget disease also have invasive ductal carcinoma or ductal carcinoma in situ (DCIS). The cancer can then spread to the dark-coloured skin around the nipple (called the areola).

Triple-negative and Basal-like Breast Cancers

Many breast cancer cells have receptors for estrogen or progesterone, and they may also have receptors for a protein called HER2 (also called ERBB2).

Triple-negative breast cancer means that the cancer cells don’t have any of these receptors.

Basal-like breast cancer is similar to triple-negative breast cancer because the cancer cells often don’t have receptors for estrogen, progesterone and HER2. But basal-like breast cancer cells have changes in the proteins that triple-negative breast cancers usually don’t have. Most basal-like breast cancers are invasive ductal carcinomas.

Most triple negative and basal breast cancers are aggressive tumours that develop rapidly and tend to spread to the brain or lungs. A proportion of women with triple negative breast cancer carry a mutation in the BRCA1 or BRCA2 gene.

Breast Cancer in Men

Men have breast tissue just like women, but their breasts are less developed. Breast cancer in men is similar to the disease in women, but there are some differences. It is currently estimated that one in 1,000 men will develop breast cancer in their lifetime. A proportion of men with breast cancer carry a mutation in the BRCA1 or BRCA2 gene.

Types of Tumours in Men

Almost all of the breast cancers found in men are ductal carcinoma (that spread). After they grow through the duct, the cancer cells can continue to grow and cause a lump or thickening in the breast. The breast cancer cells can also spread to lymph nodes and other parts of the body.

Other types of breast cancer can affect men, but they are rare. They are treated the same way as in women.

Risk Factors

Most breast cancers are attributable to many risk factors, but may affect women who do not have any of these factors:

  • Personal history
  • Family history of breast cancer and other cancers
  • Mutations in BRCA genes or other genes associated with breast cancer
  • Dense breasts
  • Reproductive history (early menstruation, late menopause, late pregnancy or no pregnancies)
  • Exposure to ionizing radiation
  • Hormone replacement therapy
  • Oral contraceptives
  • Atypical hyperplasia (abnormal breast cells)
  • Alcohol
  • Obesity
  • Physical inactivity

Screening and Diagnosis

  • Breast self-examination
  • Clinical breast examination (a thorough examination of your breasts by a qualified health professional to check for anomalies
  • Mammogram (a low-dose x-ray of your breasts)
  • Ultrasound (to find out if a mass is a solid tumour or a cyst)

Click here to visit the website of the Quebec Breast Cancer Screening Program (PQDCS).


  • Surgery: most women with breast cancer who will undergo surgery. The type of surgery offered is based on clinical assessment
  • Radiotherapy: radiation treatments direct radiation through the skin to the tumour and surrounding tissue
  • Chemotherapy: routine breast cancer treatment, both to reduce the risk of recurrence and to treat advanced cancer
  • Hormonal therapy: offered to treat cancer with positive hormone receptors.

Genetic Screening: BRCA1 and BRCA2 genes

Genetic mutations may increase the risk of certain types of cancer, but they are only attributable to 5-10% of cancers.

Breast cancer gene 1 (BRCA1) and breast cancer gene 2 (BRCA2) are normally present in the body. They are called tumour suppressor genes because they appear to play a role in controlling cancer cell growth. The presence of mutations in the BRCA1 and BRCA2 genes may make them unable to control the development of cancer. These mutations occur in around 1 in 400 people. Other genes, although less frequent, are also associated with increased risk of developing breast cancer.

Men and women can inherit a mutated BRCA gene from their mother or father. People who carry this genetic mutation can also pass it on to their children. If the mutation is present in one of two copies of a parent’s BRCA gene, a child’s risk of inheriting this genetic mutation is 50%. Note that the child has a 50% chance of not inheriting the mutation.

The probability of breast or ovarian cancer being linked to an inherited BRCA1 or BRCA2 gene mutation is highest in families where:

  • Several members have had breast or ovarian cancer
  • At least one relative had breast cancer before age 50
  • A relative has ovarian cancer
  • A relative has been diagnosed with breast and ovarian cancer
  • Members suffered cancer in both breasts
  • A male member was diagnosed with breast cancer
  • There is an Ashkenaze Jewish ancestry with a family history of breast and ovarian cancer

Studies show that women with inherited BRCA1 or BRCA2 mutations are up to 85% at risk of developing breast cancer. These women also have a higher risk of developing breast cancer at a younger age, usually before menopause.

A BRCA mutation also leads to an increased risk of cancer in both breasts. If cancer occurs in one breast, they are more likely to experience the disease in the other breast. In addition, mutations in BRCA genes increase the risk of ovarian cancer at any age and increase the risk of breast and prostate cancer in men.

Through BiogeniQ, Biron offers genetic counselling and testing to make inform decisions regarding the BRCA gene.

Quebec Breast Cancer Screening Program (PQDCS)

In order to fight breast cancer effectively, the Ministère de la Santé et des Services sociaux in Quebec, like most other Canadian provinces and several other countries, implemented the Quebec Breast Cancer Screening Program (PQDCS) in 1998. This program targets all Quebec women between the ages of 50 and 69 and invites them to undergo a mammogram every two years.

The main objective is to reduce the breast cancer mortality rate by at least 25% for women in Quebec who are screened, within the first 10 years of the program being in operation. For PQDCS, screening mammography continues to be the only screening test recognized to reduce breast cancer mortality.

To achieve this objective, the Program aims to:

  • Maximize early detection of breast cancer in the target population
  • Achieve and maintain a participation of at least 70% of Quebec women aged 50 to 69
  • Raise awareness of breast cancer issues among women in the Program and inform them about the Screening Program
  • Help women make an informed decision
  • Provide all women participating in the mammography screening program with high quality reception, support and follow-up that meets their needs and promotes their quality of life
  • Provide investigative screening and referral services in an accessible and reassuring environment that ensures the required discretion and privacy

For general information on the Quebec Breast Cancer Screening Program, you can also visit the website of the Ministère de la Santé et des Services sociaux.

Here are some of the benefits for women when they participate in the Screening Program:

  • Your letter of invitation or reminder letter will serve as a medical prescription (prescription) to schedule a mammography screening appointment
  • You will undergo your extra mammogram or tests (if necessary) in centres meeting high-quality standards
  • You will receive a result letter within 10 days of your mammogram
  • You will get quick appointments for additional examinations if necessary
  • The Program manager will ensure that a physician will follow up on the results if the mammography is abnormal
  • You will receive a reminder letter in the mail two years after your last mammogram
  • You will be participating in a quality program that is evaluated regularly

In addition to providing diagnosis services, several Imagix radiology clinics are breast cancer screening centres participating in the SDQDP.

A mammogram is the most effective test for breast cancer. Do you have doubts or questions? We will answer them.

Statistics (Public Health Agency of Canada)

  • In 2017 an estimated 26,300 Canadian women were diagnosed with breast cancer and 5,000 died of it.
  • Breast cancer accounts for approximately 26% on new cases of cancer and 13% of all cancer deaths in Canadian women.
  • 1 in 8 women are expected to develop breast cancer during her lifetime and 1 in 31 will die of it.
  • In 2009, an estimated 157,360 women were living with, or surviving from, breast cancer in Canada. That means that 1 in 107 Canadian women were diagnosed with breast cancer at some point during the 10 years prior to 2009.
  • 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, accounting for approximately 90% of all in situ breast carcinomas and 70% of all invasive breast carcinomas.

To learn more about breast cancer:

Quebec Breast Cancer Foundation

If you have any questions or need more information, please don’t hesitate to call our customer service number at 1 833 590-2715.

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