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 types of cell death. Apoptosis reflects a genetically mediated. ATP-dependent form of cell death. A passive form of cell death (oncosis) also occurs, often 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 ultrastructural analysis on paraffin-embedded material of 8 cases with "comedo"-DCIS. In each case, intraepithelial proliferation zones and intraluminal zones (peripheral and central luminal zones) were examined. All cases with "comedo"-DCIS revealed abundant apoptosis, characterized by apoptotic cells showing chromatin condensation and margination with sharply circumscribed, uniformly dense crescents, as well as cytoplasmic condensation. Numerous membrane-bound apoptotic bodies with condensed cytoplasm (with or without nuclear fragments) were also observed. The central luminal zones of "comedo"-DCIS, however, revealed necrotic debris characterized by severe degradative changes, largely devoid of recognizable cell structures. In addition, two cases displayed features of oncosis, characterized by nuclear and cytoplasmic swelling, vacuolization of cytoplasm, and mitochondrial swelling with occasional dense bodies. The results indicate that necrosis (postmortem, secondary degradative cell changes) in "comedo"-DCIS is the end result of either apoptosis (programmed cell death) alone or a combination of apoptosis and oncosis (passive or "accidental" cell death).