A thorough understanding of the different mammary gland structures and their respective physiological roles helps to detect anatomic variations and diagnose breast disease at various ages. Mammary abnormalities may be classed as either minor aberrations in normal developmental processes, as part of the breast’s cyclical activity associated with hormonal changes during the menstrual cycle, or as physiological involution of the mammary gland.

The ANDI (aberrations of normal development and involution) classification proposed by Hughes and co-workers takes into account physiological, histological and pathological findings (

table 1). The concept is based on the progression from normal to aberrant (anatomical or physiological deviation) to disease state and the distinctions between them.

This classification optimizes therapeutic strategies; when slight abnormality or aberration is diagnosed, the treatment may often be limited, whereas when complex breast disease is diagnosed, the treatment is aggressive, with surgical options.

After a brief review of the physiology of mammary development, the pathologies associated with various histological structures of breast tissue will be detailed.