Molecular and phenotypic changes in the mammary gland in different phases of life: Puberty, pregnancy and menopause

For understanding the tumorigenesis of breast cancer, it is nowadays postulated that molecular and phenotypic changes in the mammary gland in different phases of life play an important role. It is well known that the normal breast develops from infancy to puberty under the main stimuli of hormones from the pituitary gland and the ovaries. At birth, the mammary gland is build by several excretory ducts, ending in terminal ducts from which elongation and division of the alveolar buds originate. Before the onset of puberty, the alveolar buds and ducts further grow and divide in a dichotomous and sympodial manner, t…