Many terms, including duct ectasia, secretory disease, periductal mastitis, plasma cell mastitis, have been used in connection with a variety of clinical conditions associated with nipple discharge, non-puerperal sepsis and nipple retraction. The confused nomenclature reflects the uncertainties regarding the singularity or inter-relationships of the main elements--dilated ducts, periductal inflammation, bacterial infection and nipple retraction. Recent clinical studies combined with new histological and bacteriological information have set the scene for better understanding of the pathogenesis and management of these clinical conditions.