CELL RENEWAL AND FUNCTIONAL-MORPHOLOGY OF HUMAN LACTATING BREAST - PRESENTATION OF A NEW MODE OF CELL-DEATH (MAGENTOSIS) CHARACTERIZED BY NUCLEAR PERIODIC ACID-SCHIFF REACTIVITY

Cell kinetics and functional morphology of the human lactating breast were analyzed using 21 paraffin-embedded specimens of the lactating br east obtained by biopsy or surgery and two of the 'resting' breast. Fo ur types (I-IV) of lactating lobules were categorized histologically, and were well correlated with their functional status demonstrated by immunohistochemistry for epithelial membrane antigen, beta-casein, lip ase, lactoferrin, secretory component and IgA. Type I corresponded to a pre-lactating state, type II to an actively lactating state, type II I to an early stage of regression, and type IV to an advanced stage of regression, Cell proliferation monitored by Ki-67 (MIB-1) immunostain ing was at the highest level in type I lobules followed by type IV, wh ile the labeling indices were low in types II and III. Apoptosis demon strated by terminal deoxynucleotidyl transferase (TdT)-mediated deoxyu ridine triphosphate (dUTP)-biotin nick end-labeling (TUNEL) method sho wed labeling profiles comparable with the proliferative activity. Holo crine-type desquamative cells with intact-appearing nuclei were freque ntly recognized in type II lobules, in type III, a peculiar form of ce ll death, designated 'magentosis', was demonstrated. These degenerativ e cells occasionally shedding into the acinar lumen possessed homogene ous pale, TUNEL-negative nuclei with diastase-resistant periodic acid- Schiff (PAS) reactivity. 'Magentosis' specifically identified in an ea rly phase of involution of tile human lactating breast might represent a unique mode of cell death distinguishable from apoptosis and necros is.