Breast cancer: overview

Breast cancer is a disease characterized by an abnormal proliferation of the mammary gland cells. In the absence of early diagnosis, these cancer cells frequently invade adjacent tissue and spread (metastasize) via the bloodstream and the lymphatic system. The sites where breast cancer metastases are found include the bones, lungs, liver, brain, lymph nodes and cutaneous tissue. This is the leading cancer affecting women in western countries, where one woman in eleven develops breast cancer during the course of her life. It is therefore essential to be aware of this disease and to detect it at an early stage so that appropriate treatment can be provided.

The breast: a symbol of femininity

Breasts play a major role in a woman's self-image and her emotional and social life. The main natural function of the breast (mammary gland) is lactation, in other words producing milk to feed the newborn child.
Each breast is composed of a greater or lesser amount of fatty tissue which gives it shape, and contains the mammary gland made up of lobules and ducts.²

From puberty to menopause, mammary function is dependent on sex hormones — estrogen and progesterone — which are produced by the ovaries, and governed by cerebral hormones.

Their secretion is regulated by the pituitary hormones, FSH (follicle stimulating hormone) and LH (luteinizing hormone). The hypothalamus controls their release.

• Estrogens activate breast development at puberty. These hormones are produced during the first part of the menstrual cycle, after the menstrual period.
• Progesterone complements the action of estrogens. It is mostly secreted during the second part of the menstrual cycle, before the menstrual period.
• Prolactin is a hormone secreted by the pituitary gland situated in the brain. Except during breast feeding, prolactin has no effect on mammary function.