Breast Physiology: Normal and Abnormal Development and Function

The mammary gland is composed of an epithelial system of ducts and lobuloalveolar secretory units embedded in a mesenchymally derived fat pad. The growth and morphogenesis of the epithelial structures of the breast occur in various stages and are associated with concurrent hormonal changes and affected by genetic mutations. Each stage reflects the effects of systemic hormones on the glandular epithelium and also the paracrine effects of locally derived growth factors and other regulatory products produced in the stroma. Appreciating the relationship of epithelium to mesenchyme in normal growth is essential for understanding developmental abnormalities and factors that may lead to disease..