Pathological studies of apoptosis in the normal breast.

Apoptosis in the normal breast has been demonstrated to be related to the menstrual cycle. The factors that influence apoptosis in the breast are reviewed, together with related variations in the degree of apoptosis to disease pathogenesis. Evidence for a relationship between mitosis and apoptosis is provided, and the implications of pregnancy and prolonged postlactational involution are discussed. Future progress will depend on active collaboration between molecular biologists and pathologists to dissect the complex signalling pathways that appear to control the apoptotic and mitotic cascades and their inter-relationships.