Apoptotic-like tumor cells and apoptotic neutrophils in mitochondrion-rich gastric adenocarcinomas: a comparative study with light and electron microscopy between these two forms of cell death

Mitochondrion-rich adenocarcinomas represent a rare variant of gastric adenocarcinomas composed predominantly of columnar adenocarcinoma cells with eosinophilic cytoplasm, a strong supranuclear immunoreactivity for antimitochondrial antibody, and a marked neutrophil infiltration associated to tumor cell death. The purpose of this work is to investigate, using correlated light and electron microscopy, mitochondrion-rich gastric adenocarcinomas focusing on the nature of the death in neoplastic cells and in infiltrating neutrophils. Adenocarcinoma cells, single or in small clusters, showed convoluted nuclei, irregularly condensed chromatin, loss of microvilli, and nuclear envelope dilatation. No nuclear fragmentation was observed in these dying cells and the plasma membrane did not show signs of disruption. These ultrastructural findings represent intermediate aspects between apoptosis and necrosis and are compatible with apoptosis-like programmed cell death. By contrast, some infiltrating neutrophils showed ultrastructural signs of classic apoptosis such as chromatin condensation into compact geometric (globular, crescentshaped) figures, tightly packed cytoplasmic granules and intact cell membrane. Our study provides ultrastructural evidence of apoptosislike tumour cell death in mitochondrion-rich gastric carcinomas and confirms that stereotyped outcome either as apoptosis or necrosis of tumor cells cannot always be expected in human neoplasms.