Physiology and Developmental Stages of the Breast

Normal breast development is a complex process extending from the earliest stages of embryogenesis to beyond menopause. This process is driven by intrinsic genetic information, regulated by complex and tightly controlled hormonal mechanisms, and is affected by external events. Schematically, breast development is separated into prenatal, perinatal, peripubertal, adult and postmenopausal stages. Complete breast maturation does not occur until pregnancy and lactation, and thus the breast never evolves completely in nulliparous woman. Many breast diseases, benign and malignant, including breast cancer, can be better examined and explained through the spectrum of normal – or abnormal – breast development. Research is difficult due to the limited availability of human breast tissue. For this, much of our knowledge derives from mouse model studies. This information, while valuable, should be considered with caution since analogy between the mouse and human models is not perfect. Still since understanding of breast development allows better understanding of pathophysiological processes driving diseases of the breast, constant research and education is necessary not only in the sphere of basic science but also for clinicians as it allows better diagnosis and treatment for their patients.