Un cancer means the presence of abnormal cells that are multiplying in an uncontrolled fashion. In the case of breast cancer, cells can stay in the breast or spread throughout the body through blood or lymph vessels. Most of the time, the progression of breast cancer takes several months and even a few years.

Le breast cancer is the most diagnosed cancer in women around the world, both before and after menopause¹. A woman in 9 women will develop breast cancer in their lifetime and 1 in 27 women will die from it.

Most often, breast cancer occurs after 50 years. the survival rate 5 years after diagnosis ranges from 80% to 90%, depending on age and type of cancer.

The number of people affected has increased slightly but steadily over the past 3 decades. On the other hand, the mortality rate has continuously declined over the same period, thanks to the progress made in screening, diagnosis and treatment.

Let us mention that the men can also be affected; they represent 1% of all cases.

Le sein

Le breast consists of fat, glands and ducts (see diagram opposite). The glands, arranged in lobules, produce the Milk and the ducts (lactation ducts or milk ducts) serve to transport milk to the nipple. Breast tissue is influenced by hormones produced by women in varying amounts throughout their lives (puberty, pregnancy, breastfeeding, etc.). These hormones are estrogen and progesterone.

Types of breast cancer

Different types of breast cancer develop in different ways:

Non-invasive cancer

• Ductal carcinoma in situ. It is the most common type of non-invasive breast cancer in women. As the name suggests, it forms inside lactation ducts of the breast. This type of cancer has been diagnosed much more frequently with the more widespread use of mammography. Treatment for this cancer leads to a cure in almost all cases. Normally it does not spread. In exceptional cases, without treatment, he continues his growth and can then become “infiltrating” thus spreading outside the lactation ducts.

Invasive or infiltrating cancers

These forms of cancer invade the tissues around the lactation ducts, but remain inside the breast. On the other hand, if the tumor is not treated, it can spread to other parts of the body (for example, bones, lungs or liver) causing metastases.

• Ductal carcinoma. It forms in the lactation ducts. Cancer cells pass through the wall of the ducts;
• Lobular carcinoma. Cancer cells appear in lobules grouped together in the lobes. Then, they cross the wall of the lobules and disseminate in the surrounding tissues;
• Inflammatory carcinoma. A rare cancer that is mainly characterized by a breast that can become red, swollen et chaud. The skin of the breast can also take on the appearance of an orange peel. This type of cancer progresses faster and is more difficult to treat;
• Other carcinomas (medullary, colloid or mucinous, tubular, papillary). These types of breast cancer are rarer. The main differences between these types of cancer are based on the type of cells affected;
• Paget’s disease. A rare cancer that manifests as a small wound to the nipple that does not heal.

Causes

There are several known risk factors for breast cancer. However, in most cases it is impossible to explain the reasons for its occurrence in a particular person.

benefits mutations in genes, passed on from generation to generation or acquired over a lifetime (exposure to radiation or certain toxic chemicals, for example, can change genes), can cause breast cancer. The BRCA1 and BRCA2 genes, for example, are genes for susceptibility to breast and ovarian cancers. Women who carry mutations in these genes have a very high risk of cancer.

Evolution

The chances of healing depend on the type of cancer and its stage of development when you start treatment. Various factors influence the speed to which a tumor will grow. To find out more about the stages in the development of cancer, see our Cancer fact sheet.