A comprehensive summary of the current knowledge of breast diseases for practicing clinicians and basic scientists, including clinical features, management, and underlying biological and epidemiological factors. The coverage includes not only breast cancer, but also the various benign diseases of the breast, their management, and their relationship to subsequent breast cancer development. Information is presented about the early detection and management of breast cancer using surgery, radiation therapy, and systemic therapies, including chemotherapy and hormonal interventions. The rapid advances in the understanding of the molecular biology and genetics of both normal tissues and cancers are also detailed, in a form accessible to clinicians.