Mammary "comedo"-DCIS: Apoptosis, oncosis, and necrosis: An electron microscopic examination of 8 cases

The terms apoptosis and necrosis are commonly used to imply two distinct ty pes of cell death. Apoptosis reflects a genetically mediated, ATP-dependent form of cell death. A passive form of cell death (oncosis) also occurs, of ten in response to some form of injury. Both pathways can lead to necrosis (postmortem autolytic cell changes). The nature of intraluminal necrosis in mammary ductal carcinoma in situ (DCIS) was evaluated using ultrastructura l analysis on paraffin-embedded material of 8 cases with "comedo"-DCIS. In each case, intraepithelial proliferation zones and intraluminal zones (peri pheral and central luminal zones) were examined. All cases with "comedo"-DC IS revealed abundant apoptosis, characterized by apoptotic cells showing ch romatin condensation and margination with sharply circumscribed, uniformly dense crescents, as well as cytoplasmic condensation. Numerous membrane-bou nd apoptotic bodies with condensed cytoplasm (with or without nuclear fragm ents) were also observed. The central luminal zones of "comedo"-DCIS, howev er, revealed necrotic debris characterized by severe degradative changes, l argely devoid of recognizable cell structures. In addition, two cases displ ayed features of oncosis, characterized by nuclear and cytoplasmic swelling , vacuolization of cytoplasm, and mitochondrial swelling with occasional de nse bodies. The results indicate that necrosis (postmortem, secondary degra dative cell changes) in "comedo"-DCIS is the end result of either apoptosis (programmed cell death) alone or a combination of apoptosis and oncosis (p assive or "accidental" cell death).